[DevTools] Make DevTools clients talk directly to DevToolsAgentHost instead of using DevToolsManager.

Previously, client used methods on DevToolsManager passing |this| to most of them.
Instead, it should hold a scoped_refptr to inspected DevToolsAgentHost and talk
to it directly. This creates a single clean entry point for the client, and allows
in the future to handle browser-wide protocol messages and debug multiple hosts at once.

BUG=401073
TBR=kalman@chromium.org

Review URL: https://codereview.chromium.org/449043002

Cr-Commit-Position: refs/heads/master@{#288452}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288452 0039d316-1c4b-4281-b951-d872f2087c98

44 files changed, 453 insertions, 685 deletions

diff --git a/apps/app_window_registry.cc b/apps/app_window_registry.cc
index 67c836a..79a3373 100644
--- a/apps/app_window_registry.cc
+++ b/apps/app_window_registry.cc
@@ -13,7 +13,6 @@
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/site_instance.h"
@@ -72,13 +71,11 @@ AppWindowRegistry::AppWindowRegistry(content::BrowserContext* context)
     : context_(context),
       devtools_callback_(base::Bind(&AppWindowRegistry::OnDevToolsStateChanged,
                                     base::Unretained(this))) {
-  content::DevToolsManager::GetInstance()->AddAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::AddAgentStateCallback(devtools_callback_);
 }
 
 AppWindowRegistry::~AppWindowRegistry() {
-  content::DevToolsManager::GetInstance()->RemoveAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::RemoveAgentStateCallback(devtools_callback_);
 }
 
 // static
diff --git a/chrome/browser/devtools/chrome_devtools_manager_delegate.cc b/chrome/browser/devtools/chrome_devtools_manager_delegate.cc
index d5751a8..87faad6 100644
--- a/chrome/browser/devtools/chrome_devtools_manager_delegate.cc
+++ b/chrome/browser/devtools/chrome_devtools_manager_delegate.cc
@@ -13,7 +13,6 @@
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/site_instance.h"
diff --git a/chrome/browser/devtools/devtools_sanity_browsertest.cc b/chrome/browser/devtools/devtools_sanity_browsertest.cc
index 698cc8c..ccfec84 100644
--- a/chrome/browser/devtools/devtools_sanity_browsertest.cc
+++ b/chrome/browser/devtools/devtools_sanity_browsertest.cc
@@ -37,9 +37,7 @@
 #include "content/public/browser/child_process_data.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_http_handler.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
@@ -55,7 +53,6 @@
 #include "net/test/spawned_test_server/spawned_test_server.h"
 
 using content::BrowserThread;
-using content::DevToolsManager;
 using content::DevToolsAgentHost;
 using content::NavigationController;
 using content::RenderViewHost;
diff --git a/chrome/browser/devtools/devtools_ui_bindings.cc b/chrome/browser/devtools/devtools_ui_bindings.cc
index f40ed89..b8f6087 100644
--- a/chrome/browser/devtools/devtools_ui_bindings.cc
+++ b/chrome/browser/devtools/devtools_ui_bindings.cc
@@ -32,8 +32,6 @@
 #include "chrome/common/url_constants.h"
 #include "components/infobars/core/confirm_infobar_delegate.h"
 #include "components/infobars/core/infobar.h"
-#include "content/public/browser/devtools_client_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/favicon_status.h"
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/navigation_controller.h"
@@ -261,8 +259,8 @@ void DevToolsUIBindings::FrontendWebContentsObserver::RenderProcessGone(
     case base::TERMINATION_STATUS_ABNORMAL_TERMINATION:
     case base::TERMINATION_STATUS_PROCESS_WAS_KILLED:
     case base::TERMINATION_STATUS_PROCESS_CRASHED:
-      content::DevToolsManager::GetInstance()->ClientHostClosing(
-          devtools_bindings_);
+      if (devtools_bindings_->agent_host_)
+        devtools_bindings_->Detach();
       break;
     default:
       break;
@@ -351,7 +349,8 @@ DevToolsUIBindings::DevToolsUIBindings(content::WebContents* web_contents,
 }
 
 DevToolsUIBindings::~DevToolsUIBindings() {
-  content::DevToolsManager::GetInstance()->ClientHostClosing(this);
+  if (agent_host_)
+    agent_host_->DetachClient();
 
   for (IndexingJobsMap::const_iterator jobs_it(indexing_jobs_.begin());
        jobs_it != indexing_jobs_.end(); ++jobs_it) {
@@ -403,25 +402,27 @@ void DevToolsUIBindings::HandleMessageFromDevToolsFrontend(
 
 void DevToolsUIBindings::HandleMessageFromDevToolsFrontendToBackend(
     const std::string& message) {
-  content::DevToolsManager::GetInstance()->DispatchOnInspectorBackend(
-      this, message);
+  if (agent_host_)
+    agent_host_->DispatchProtocolMessage(message);
 }
 
-// content::DevToolsClientHost implementation ---------------------------------
-void DevToolsUIBindings::DispatchOnInspectorFrontend(
-    const std::string& message) {
+// content::DevToolsAgentHostClient implementation --------------------------
+void DevToolsUIBindings::DispatchProtocolMessage(
+    content::DevToolsAgentHost* agent_host, const std::string& message) {
+  DCHECK(agent_host == agent_host_.get());
   base::StringValue message_value(message);
   CallClientFunction("InspectorFrontendAPI.dispatchMessage",
                      &message_value, NULL, NULL);
 }
 
-void DevToolsUIBindings::InspectedContentsClosing() {
+void DevToolsUIBindings::AgentHostClosed(
+    content::DevToolsAgentHost* agent_host,
+    bool replaced_with_another_client) {
+  DCHECK(agent_host == agent_host_.get());
+  agent_host_ = NULL;
   delegate_->InspectedContentsClosing();
 }
 
-void DevToolsUIBindings::ReplacedWithAnotherClient() {
-}
-
 // DevToolsEmbedderMessageDispatcher::Delegate implementation -----------------
 void DevToolsUIBindings::ActivateWindow() {
   delegate_->ActivateWindow();
@@ -625,8 +626,8 @@ void DevToolsUIBindings::SetDevicesUpdatesEnabled(bool enabled) {
 }
 
 void DevToolsUIBindings::SendMessageToBrowser(const std::string& message) {
-  content::DevToolsManager::GetInstance()->DispatchOnInspectorBackend(
-      this, message);
+  if (agent_host_)
+    agent_host_->DispatchProtocolMessage(message);
 }
 
 void DevToolsUIBindings::DeviceCountChanged(int count) {
@@ -780,6 +781,28 @@ void DevToolsUIBindings::SetDelegate(Delegate* delegate) {
   delegate_.reset(delegate);
 }
 
+void DevToolsUIBindings::AttachTo(content::DevToolsAgentHost* agent_host) {
+  DCHECK(!agent_host_);
+  agent_host_ = agent_host;
+  agent_host_->AttachClient(this);
+}
+
+void DevToolsUIBindings::Reattach() {
+  DCHECK(agent_host_);
+  agent_host_->DetachClient();
+  agent_host_->AttachClient(this);
+}
+
+void DevToolsUIBindings::Detach() {
+  DCHECK(agent_host_);
+  agent_host_->DetachClient();
+  agent_host_ = NULL;
+}
+
+bool DevToolsUIBindings::IsAttachedTo(content::DevToolsAgentHost* agent_host) {
+  return agent_host_ == agent_host;
+}
+
 void DevToolsUIBindings::CallClientFunction(const std::string& function_name,
                                             const base::Value* arg1,
                                             const base::Value* arg2,
diff --git a/chrome/browser/devtools/devtools_ui_bindings.h b/chrome/browser/devtools/devtools_ui_bindings.h
index 2c47ea7..9205ca5 100644
--- a/chrome/browser/devtools/devtools_ui_bindings.h
+++ b/chrome/browser/devtools/devtools_ui_bindings.h
@@ -17,7 +17,7 @@
 #include "chrome/browser/devtools/devtools_file_helper.h"
 #include "chrome/browser/devtools/devtools_file_system_indexer.h"
 #include "chrome/browser/devtools/devtools_targets_ui.h"
-#include "content/public/browser/devtools_client_host.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/devtools_frontend_host.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -27,7 +27,6 @@ class InfoBarService;
 class Profile;
 
 namespace content {
-class DevToolsClientHost;
 struct FileChooserParams;
 class WebContents;
 }
@@ -37,7 +36,7 @@ class DevToolsUIBindings : public content::NotificationObserver,
                            public content::DevToolsFrontendHost::Delegate,
                            public DevToolsEmbedderMessageDispatcher::Delegate,
                            public DevToolsAndroidBridge::DeviceCountListener,
-                           public content::DevToolsClientHost {
+                           public content::DevToolsAgentHostClient {
  public:
   static GURL ApplyThemeToURL(Profile* profile, const GURL& base_url);
 
@@ -64,6 +63,7 @@ class DevToolsUIBindings : public content::NotificationObserver,
 
   content::WebContents* web_contents() { return web_contents_; }
   Profile* profile() { return profile_; }
+  content::DevToolsAgentHost* agent_host() { return agent_host_.get(); }
 
   // Takes ownership over the |delegate|.
   void SetDelegate(Delegate* delegate);
@@ -71,6 +71,11 @@ class DevToolsUIBindings : public content::NotificationObserver,
                           const base::Value* arg1,
                           const base::Value* arg2,
                           const base::Value* arg3);
+  void AttachTo(content::DevToolsAgentHost* agent_host);
+  void Reattach();
+  void Detach();
+  bool IsAttachedTo(content::DevToolsAgentHost* agent_host);
+
  private:
   // content::NotificationObserver overrides.
   virtual void Observe(int type,
@@ -83,10 +88,13 @@ class DevToolsUIBindings : public content::NotificationObserver,
   virtual void HandleMessageFromDevToolsFrontendToBackend(
       const std::string& message) OVERRIDE;
 
-  // content::DevToolsClientHost implementation.
-  virtual void DispatchOnInspectorFrontend(const std::string& message) OVERRIDE;
-  virtual void InspectedContentsClosing() OVERRIDE;
-  virtual void ReplacedWithAnotherClient() OVERRIDE;
+  // content::DevToolsAgentHostClient implementation.
+  virtual void DispatchProtocolMessage(
+      content::DevToolsAgentHost* agent_host,
+      const std::string& message) OVERRIDE;
+  virtual void AgentHostClosed(
+       content::DevToolsAgentHost* agent_host,
+       bool replaced_with_another_client) OVERRIDE;
 
   // DevToolsEmbedderMessageDispatcher::Delegate implementation.
   virtual void ActivateWindow() OVERRIDE;
@@ -166,6 +174,7 @@ class DevToolsUIBindings : public content::NotificationObserver,
   Profile* profile_;
   content::WebContents* web_contents_;
   scoped_ptr<Delegate> delegate_;
+  scoped_refptr<content::DevToolsAgentHost> agent_host_;
   content::NotificationRegistrar registrar_;
   scoped_ptr<content::DevToolsFrontendHost> frontend_host_;
   scoped_ptr<DevToolsFileHelper> file_helper_;
diff --git a/chrome/browser/devtools/devtools_window.cc b/chrome/browser/devtools/devtools_window.cc
index e4445e3..8e4fc52 100644
--- a/chrome/browser/devtools/devtools_window.cc
+++ b/chrome/browser/devtools/devtools_window.cc
@@ -34,8 +34,6 @@
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/navigation_entry.h"
@@ -425,9 +423,7 @@ DevToolsWindow* DevToolsWindow::OpenDevToolsWindowForWorker(
   DevToolsWindow* window = FindDevToolsWindow(worker_agent);
   if (!window) {
     window = DevToolsWindow::CreateDevToolsWindowForWorker(profile);
-    // Will disconnect the current client host if there is one.
-    content::DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-        worker_agent, window->bindings_);
+    window->bindings_->AttachTo(worker_agent);
   }
   window->ScheduleShow(DevToolsToggleAction::Show());
   return window;
@@ -479,8 +475,7 @@ void DevToolsWindow::OpenExternalFrontend(
   if (!window) {
     window = Create(profile, DevToolsUI::GetProxyURL(frontend_url), NULL,
                     false, true, false, "");
-    content::DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-        agent_host, window->bindings_);
+    window->bindings_->AttachTo(agent_host);
   }
   window->ScheduleShow(DevToolsToggleAction::Show());
 }
@@ -493,7 +488,6 @@ DevToolsWindow* DevToolsWindow::ToggleDevToolsWindow(
     const std::string& settings) {
   scoped_refptr<DevToolsAgentHost> agent(
       DevToolsAgentHost::GetOrCreateFor(inspected_web_contents));
-  content::DevToolsManager* manager = content::DevToolsManager::GetInstance();
   DevToolsWindow* window = FindDevToolsWindow(agent.get());
   bool do_open = force_open;
   if (!window) {
@@ -503,7 +497,7 @@ DevToolsWindow* DevToolsWindow::ToggleDevToolsWindow(
         base::UserMetricsAction("DevTools_InspectRenderer"));
     window = Create(
         profile, GURL(), inspected_web_contents, false, false, true, settings);
-    manager->RegisterDevToolsClientHostFor(agent.get(), window->bindings_);
+    window->bindings_->AttachTo(agent.get());
     do_open = true;
   }
 
@@ -793,10 +787,9 @@ DevToolsWindow* DevToolsWindow::FindDevToolsWindow(
   if (!agent_host || g_instances == NULL)
     return NULL;
   DevToolsWindows* instances = g_instances.Pointer();
-  content::DevToolsManager* manager = content::DevToolsManager::GetInstance();
   for (DevToolsWindows::iterator it(instances->begin()); it != instances->end();
        ++it) {
-    if (manager->GetDevToolsAgentHostFor((*it)->bindings_) == agent_host)
+    if ((*it)->bindings_->IsAttachedTo(agent_host))
       return *it;
   }
   return NULL;
@@ -826,14 +819,7 @@ WebContents* DevToolsWindow::OpenURLFromTab(
         inspected_web_contents->OpenURL(params) : NULL;
   }
 
-  content::DevToolsManager* manager = content::DevToolsManager::GetInstance();
-  scoped_refptr<DevToolsAgentHost> agent_host(
-      manager->GetDevToolsAgentHostFor(bindings_));
-  if (!agent_host.get())
-    return NULL;
-  manager->ClientHostClosing(bindings_);
-  manager->RegisterDevToolsClientHostFor(agent_host.get(),
-                                         bindings_);
+  bindings_->Reattach();
 
   content::NavigationController::LoadURLParams load_url_params(params.url);
   main_web_contents_->GetController().LoadURLWithParams(load_url_params);
@@ -910,10 +896,8 @@ void DevToolsWindow::BeforeUnloadFired(WebContents* tab,
                                        bool* proceed_to_fire_unload) {
   if (!intercepted_page_beforeunload_) {
     // Docked devtools window closed directly.
-    if (proceed) {
-      content::DevToolsManager::GetInstance()->ClientHostClosing(
-          bindings_);
-    }
+    if (proceed)
+      bindings_->Detach();
     *proceed_to_fire_unload = proceed;
   } else {
     // Inspected page is attempting to close.
diff --git a/chrome/browser/extensions/api/debugger/debugger_api.cc b/chrome/browser/extensions/api/debugger/debugger_api.cc
index aaf3b94..1bacc59 100644
--- a/chrome/browser/extensions/api/debugger/debugger_api.cc
+++ b/chrome/browser/extensions/api/debugger/debugger_api.cc
@@ -31,9 +31,7 @@
 #include "components/infobars/core/confirm_infobar_delegate.h"
 #include "components/infobars/core/infobar.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_http_handler.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/render_process_host.h"
@@ -57,9 +55,7 @@
 #include "ui/base/l10n/l10n_util.h"
 
 using content::DevToolsAgentHost;
-using content::DevToolsClientHost;
 using content::DevToolsHttpHandler;
-using content::DevToolsManager;
 using content::RenderProcessHost;
 using content::RenderViewHost;
 using content::RenderWidgetHost;
@@ -77,7 +73,7 @@ class ExtensionRegistry;
 
 // ExtensionDevToolsClientHost ------------------------------------------------
 
-class ExtensionDevToolsClientHost : public DevToolsClientHost,
+class ExtensionDevToolsClientHost : public content::DevToolsAgentHostClient,
                                     public content::NotificationObserver,
                                     public ExtensionRegistryObserver {
  public:
@@ -91,6 +87,7 @@ class ExtensionDevToolsClientHost : public DevToolsClientHost,
   virtual ~ExtensionDevToolsClientHost();
 
   const std::string& extension_id() { return extension_id_; }
+  DevToolsAgentHost* agent_host() { return agent_host_.get(); }
   void Close();
   void SendMessageToBackend(DebuggerSendCommandFunction* function,
                             const std::string& method,
@@ -99,10 +96,13 @@ class ExtensionDevToolsClientHost : public DevToolsClientHost,
   // Marks connection as to-be-terminated by the user.
   void MarkAsDismissed();
 
-  // DevToolsClientHost interface
-  virtual void InspectedContentsClosing() OVERRIDE;
-  virtual void DispatchOnInspectorFrontend(const std::string& message) OVERRIDE;
-  virtual void ReplacedWithAnotherClient() OVERRIDE;
+  // DevToolsAgentHostClient interface.
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host,
+      bool replaced_with_another_client) OVERRIDE;
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host,
+      const std::string& message) OVERRIDE;
 
  private:
   void SendDetachedEvent();
@@ -289,11 +289,10 @@ void AttachedClientHosts::Remove(ExtensionDevToolsClientHost* client_host) {
 ExtensionDevToolsClientHost* AttachedClientHosts::Lookup(
     DevToolsAgentHost* agent_host,
     const std::string& extension_id) {
-  DevToolsManager* manager = DevToolsManager::GetInstance();
   for (ClientHosts::iterator it = client_hosts_.begin();
        it != client_hosts_.end(); ++it) {
     ExtensionDevToolsClientHost* client_host = *it;
-    if (manager->GetDevToolsAgentHostFor(client_host) == agent_host &&
+    if (client_host->agent_host() == agent_host &&
         client_host->extension_id() == extension_id)
       return client_host;
   }
@@ -334,8 +333,7 @@ ExtensionDevToolsClientHost::ExtensionDevToolsClientHost(
                  content::NotificationService::AllSources());
 
   // Attach to debugger and tell it we are ready.
-  DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-      agent_host_.get(), this);
+  agent_host_->AttachClient(this);
 
   if (infobar_) {
     static_cast<ExtensionDevToolsInfoBarDelegate*>(
@@ -363,18 +361,18 @@ ExtensionDevToolsClientHost::~ExtensionDevToolsClientHost() {
   AttachedClientHosts::GetInstance()->Remove(this);
 }
 
-// DevToolsClientHost interface
-void ExtensionDevToolsClientHost::InspectedContentsClosing() {
+// DevToolsAgentHostClient implementation.
+void ExtensionDevToolsClientHost::AgentHostClosed(
+    DevToolsAgentHost* agent_host, bool replaced_with_another_client) {
+  DCHECK(agent_host == agent_host_.get());
+  if (replaced_with_another_client)
+    detach_reason_ = OnDetach::REASON_REPLACED_WITH_DEVTOOLS;
   SendDetachedEvent();
   delete this;
 }
 
-void ExtensionDevToolsClientHost::ReplacedWithAnotherClient() {
-  detach_reason_ = OnDetach::REASON_REPLACED_WITH_DEVTOOLS;
-}
-
 void ExtensionDevToolsClientHost::Close() {
-  DevToolsManager::GetInstance()->ClientHostClosing(this);
+  agent_host_->DetachClient();
   delete this;
 }
 
@@ -394,7 +392,7 @@ void ExtensionDevToolsClientHost::SendMessageToBackend(
 
   std::string json_args;
   base::JSONWriter::Write(&protocol_request, &json_args);
-  DevToolsManager::GetInstance()->DispatchOnInspectorBackend(this, json_args);
+  agent_host_->DispatchProtocolMessage(json_args);
 }
 
 void ExtensionDevToolsClientHost::MarkAsDismissed() {
@@ -442,8 +440,9 @@ void ExtensionDevToolsClientHost::Observe(
   }
 }
 
-void ExtensionDevToolsClientHost::DispatchOnInspectorFrontend(
-    const std::string& message) {
+void ExtensionDevToolsClientHost::DispatchProtocolMessage(
+    DevToolsAgentHost* agent_host, const std::string& message) {
+  DCHECK(agent_host == agent_host_.get());
   if (!EventRouter::Get(profile_))
     return;
 
diff --git a/chrome/browser/prerender/prerender_browsertest.cc b/chrome/browser/prerender/prerender_browsertest.cc
index 02c7232..4c96662 100644
--- a/chrome/browser/prerender/prerender_browsertest.cc
+++ b/chrome/browser/prerender/prerender_browsertest.cc
@@ -67,8 +67,6 @@
 #include "chrome/test/base/uma_histogram_helper.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/notification_service.h"
@@ -100,8 +98,6 @@
 
 using content::BrowserThread;
 using content::DevToolsAgentHost;
-using content::DevToolsClientHost;
-using content::DevToolsManager;
 using content::NavigationController;
 using content::OpenURLParams;
 using content::Referrer;
@@ -746,13 +742,14 @@ class TestSafeBrowsingServiceFactory : public SafeBrowsingServiceFactory {
 };
 #endif
 
-class FakeDevToolsClientHost : public DevToolsClientHost {
+class FakeDevToolsClient : public content::DevToolsAgentHostClient {
  public:
-  FakeDevToolsClientHost() {}
-  virtual ~FakeDevToolsClientHost() {}
-  virtual void InspectedContentsClosing() OVERRIDE {}
-  virtual void DispatchOnInspectorFrontend(const std::string& msg) OVERRIDE {}
-  virtual void ReplacedWithAnotherClient() OVERRIDE {}
+  FakeDevToolsClient() {}
+  virtual ~FakeDevToolsClient() {}
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE {}
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host, bool replaced) OVERRIDE {}
 };
 
 class RestorePrerenderMode {
@@ -3297,13 +3294,12 @@ IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest,
       current_browser()->tab_strip_model()->GetActiveWebContents();
   scoped_refptr<DevToolsAgentHost> agent(
       DevToolsAgentHost::GetOrCreateFor(web_contents));
-  DevToolsManager* manager = DevToolsManager::GetInstance();
-  FakeDevToolsClientHost client_host;
-  manager->RegisterDevToolsClientHostFor(agent.get(), &client_host);
+  FakeDevToolsClient client;
+  agent->AttachClient(&client);
   const char* url = "files/prerender/prerender_page.html";
   PrerenderTestURL(url, FINAL_STATUS_DEVTOOLS_ATTACHED, 1);
   NavigateToURLWithDisposition(url, CURRENT_TAB, false);
-  manager->ClientHostClosing(&client_host);
+  agent->DetachClient();
 }
 
 // Validate that the sessionStorage namespace remains the same when swapping
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 2f13de8..ac3ae9c 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -156,7 +156,7 @@
 #include "components/startup_metric_utils/startup_metric_utils.h"
 #include "components/web_modal/popup_manager.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
-#include "content/public/browser/devtools_manager.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/browser/interstitial_page.h"
@@ -2028,7 +2028,7 @@ void Browser::Observe(int type,
 
 void Browser::OnDevToolsDisabledChanged() {
   if (profile_->GetPrefs()->GetBoolean(prefs::kDevToolsDisabled))
-    content::DevToolsManager::GetInstance()->CloseAllClientHosts();
+    content::DevToolsAgentHost::DetachAllClients();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu_controller_browsertest.mm b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu_controller_browsertest.mm
index 2f8fa91..0d6cf51 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_action_context_menu_controller_browsertest.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_action_context_menu_controller_browsertest.mm
@@ -22,7 +22,7 @@
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/pref_names.h"
-#include "content/public/browser/devtools_manager.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/test/test_utils.h"
 #include "extensions/common/extension.h"
 #include "grit/generated_resources.h"
@@ -147,13 +147,11 @@ class DevToolsAttachedObserver {
         devtools_callback_(base::Bind(
             &DevToolsAttachedObserver::OnDevToolsStateChanged,
             base::Unretained(this))) {
-    content::DevToolsManager::GetInstance()->AddAgentStateCallback(
-        devtools_callback_);
+    content::DevToolsAgentHost::AddAgentStateCallback(devtools_callback_);
   }
 
   ~DevToolsAttachedObserver() {
-    content::DevToolsManager::GetInstance()->RemoveAgentStateCallback(
-        devtools_callback_);
+    content::DevToolsAgentHost::RemoveAgentStateCallback(devtools_callback_);
   }
 
   void OnDevToolsStateChanged(content::DevToolsAgentHost*, bool attached) {
diff --git a/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm b/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
index 814f202..b5dbd4e 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
@@ -20,7 +20,6 @@
 #import "chrome/browser/ui/cocoa/info_bubble_window.h"
 #include "components/web_modal/popup_manager.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
@@ -97,13 +96,11 @@ class DevtoolsNotificationBridge : public content::NotificationObserver {
       devtools_callback_(base::Bind(
           &DevtoolsNotificationBridge::OnDevToolsStateChanged,
           base::Unretained(this))) {
-    content::DevToolsManager::GetInstance()->AddAgentStateCallback(
-        devtools_callback_);
+    content::DevToolsAgentHost::AddAgentStateCallback(devtools_callback_);
   }
 
   virtual ~DevtoolsNotificationBridge() {
-    content::DevToolsManager::GetInstance()->RemoveAgentStateCallback(
-        devtools_callback_);
+    content::DevToolsAgentHost::RemoveAgentStateCallback(devtools_callback_);
   }
 
   void OnDevToolsStateChanged(content::DevToolsAgentHost* agent_host,
diff --git a/chrome/browser/ui/views/extensions/extension_popup.cc b/chrome/browser/ui/views/extensions/extension_popup.cc
index e77df9e..ad8511d 100644
--- a/chrome/browser/ui/views/extensions/extension_popup.cc
+++ b/chrome/browser/ui/views/extensions/extension_popup.cc
@@ -12,7 +12,6 @@
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/render_view_host.h"
@@ -69,15 +68,13 @@ ExtensionPopup::ExtensionPopup(extensions::ExtensionViewHost* host,
       this,
       extensions::NOTIFICATION_EXTENSION_HOST_VIEW_SHOULD_CLOSE,
       content::Source<content::BrowserContext>(host->browser_context()));
-  content::DevToolsManager::GetInstance()->AddAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::AddAgentStateCallback(devtools_callback_);
 
   GetExtensionView(host)->GetBrowser()->tab_strip_model()->AddObserver(this);
 }
 
 ExtensionPopup::~ExtensionPopup() {
-  content::DevToolsManager::GetInstance()->RemoveAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::RemoveAgentStateCallback(devtools_callback_);
 
   GetExtensionView(
       host_.get())->GetBrowser()->tab_strip_model()->RemoveObserver(this);
diff --git a/chrome/browser/ui/webui/inspect_ui.cc b/chrome/browser/ui/webui/inspect_ui.cc
index dc203b6..6624e41 100644
--- a/chrome/browser/ui/webui/inspect_ui.cc
+++ b/chrome/browser/ui/webui/inspect_ui.cc
@@ -16,7 +16,6 @@
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
@@ -292,10 +291,7 @@ void InspectUI::InspectBrowserWithCustomFrontend(
   // Install devtools bindings.
   DevToolsUIBindings* bindings = new DevToolsUIBindings(front_end,
                                                         frontend_url);
-
-  // Engage remote debugging between front-end and agent host.
-  content::DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-      agent_host, bindings);
+  bindings->AttachTo(agent_host.get());
 }
 
 void InspectUI::InspectDevices(Browser* browser) {
diff --git a/chrome/browser/ui/webui/interstitials/interstitial_ui_browsertest.cc b/chrome/browser/ui/webui/interstitials/interstitial_ui_browsertest.cc
index 8047d03..1f06023 100644
--- a/chrome/browser/ui/webui/interstitials/interstitial_ui_browsertest.cc
+++ b/chrome/browser/ui/webui/interstitials/interstitial_ui_browsertest.cc
@@ -10,7 +10,6 @@
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/web_contents.h"
 
 class InterstitialUITest : public InProcessBrowserTest {
diff --git a/content/browser/devtools/devtools_agent_host_impl.cc b/content/browser/devtools/devtools_agent_host_impl.cc
index 9d4e707..1309eac 100644
--- a/content/browser/devtools/devtools_agent_host_impl.cc
+++ b/content/browser/devtools/devtools_agent_host_impl.cc
@@ -5,6 +5,7 @@
 #include "content/browser/devtools/devtools_agent_host_impl.h"
 
 #include <map>
+#include <vector>
 
 #include "base/basictypes.h"
 #include "base/guid.h"
@@ -12,17 +13,23 @@
 #include "content/browser/devtools/devtools_manager_impl.h"
 #include "content/browser/devtools/forwarding_agent_host.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/devtools_manager_delegate.h"
 
 namespace content {
 
 namespace {
 typedef std::map<std::string, DevToolsAgentHostImpl*> Instances;
 base::LazyInstance<Instances>::Leaky g_instances = LAZY_INSTANCE_INITIALIZER;
+
+typedef std::vector<const DevToolsAgentHost::AgentStateCallback*>
+    AgentStateCallbacks;
+base::LazyInstance<AgentStateCallbacks>::Leaky g_callbacks =
+    LAZY_INSTANCE_INITIALIZER;
 }  // namespace
 
 DevToolsAgentHostImpl::DevToolsAgentHostImpl()
-    : close_listener_(NULL),
-      id_(base::GenerateGUID()) {
+    : id_(base::GenerateGUID()),
+      client_(NULL) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   g_instances.Get()[id_] = this;
 }
@@ -49,8 +56,30 @@ scoped_refptr<DevToolsAgentHost> DevToolsAgentHost::Create(
   return new ForwardingAgentHost(delegate);
 }
 
+void DevToolsAgentHostImpl::AttachClient(DevToolsAgentHostClient* client) {
+  scoped_refptr<DevToolsAgentHostImpl> protect(this);
+  if (client_) {
+    client_->AgentHostClosed(this, true);
+    Detach();
+  } else {
+    DevToolsManagerImpl::GetInstance()->OnClientAttached();
+  }
+  client_ = client;
+  Attach();
+}
+
+void DevToolsAgentHostImpl::DetachClient() {
+  if (!client_)
+    return;
+
+  scoped_refptr<DevToolsAgentHostImpl> protect(this);
+  client_ = NULL;
+  Detach();
+  DevToolsManagerImpl::GetInstance()->OnClientDetached();
+}
+
 bool DevToolsAgentHostImpl::IsAttached() {
-  return !!DevToolsManagerImpl::GetInstance()->GetDevToolsClientHostFor(this);
+  return !!client_;
 }
 
 void DevToolsAgentHostImpl::InspectElement(int x, int y) {
@@ -74,12 +103,76 @@ bool DevToolsAgentHostImpl::IsWorker() const {
   return false;
 }
 
-void DevToolsAgentHostImpl::NotifyCloseListener() {
-  if (close_listener_) {
-    scoped_refptr<DevToolsAgentHostImpl> protect(this);
-    close_listener_->AgentHostClosing(this);
-    close_listener_ = NULL;
+void DevToolsAgentHostImpl::HostClosed() {
+  if (!client_)
+    return;
+
+  scoped_refptr<DevToolsAgentHostImpl> protect(this);
+  client_->AgentHostClosed(this, false);
+  client_ = NULL;
+  DevToolsManagerImpl::GetInstance()->OnClientDetached();
+}
+
+void DevToolsAgentHostImpl::SendMessageToClient(const std::string& message) {
+  if (!client_)
+    return;
+  client_->DispatchProtocolMessage(this, message);
+}
+
+// static
+void DevToolsAgentHost::DetachAllClients() {
+  if (g_instances == NULL)
+    return;
+
+  // Make a copy, since detaching may lead to agent destruction, which
+  // removes it from the instances.
+  Instances copy = g_instances.Get();
+  for (Instances::iterator it(copy.begin()); it != copy.end(); ++it) {
+    DevToolsAgentHostImpl* agent_host = it->second;
+    if (agent_host->client_) {
+      scoped_refptr<DevToolsAgentHostImpl> protect(agent_host);
+      agent_host->client_->AgentHostClosed(agent_host, true);
+      agent_host->client_ = NULL;
+      agent_host->Detach();
+      DevToolsManagerImpl::GetInstance()->OnClientDetached();
+    }
   }
 }
 
+// static
+void DevToolsAgentHost::AddAgentStateCallback(
+    const AgentStateCallback& callback) {
+  g_callbacks.Get().push_back(&callback);
+}
+
+// static
+void DevToolsAgentHost::RemoveAgentStateCallback(
+    const AgentStateCallback& callback) {
+  if (g_callbacks == NULL)
+    return;
+
+  AgentStateCallbacks* callbacks_ = g_callbacks.Pointer();
+  AgentStateCallbacks::iterator it =
+      std::find(callbacks_->begin(), callbacks_->end(), &callback);
+  DCHECK(it != callbacks_->end());
+  callbacks_->erase(it);
+}
+
+// static
+void DevToolsAgentHostImpl::NotifyCallbacks(
+    DevToolsAgentHostImpl* agent_host, bool attached) {
+  AgentStateCallbacks copy(g_callbacks.Get());
+  DevToolsManagerImpl* manager = DevToolsManagerImpl::GetInstance();
+  if (manager->delegate())
+    manager->delegate()->DevToolsAgentStateChanged(agent_host, attached);
+  for (AgentStateCallbacks::iterator it = copy.begin(); it != copy.end(); ++it)
+     (*it)->Run(agent_host, attached);
+}
+
+void DevToolsAgentHostImpl::Inspect(BrowserContext* browser_context) {
+  DevToolsManagerImpl* manager = DevToolsManagerImpl::GetInstance();
+  if (manager->delegate())
+    manager->delegate()->Inspect(browser_context, this);
+}
+
 }  // namespace content
diff --git a/content/browser/devtools/devtools_agent_host_impl.h b/content/browser/devtools/devtools_agent_host_impl.h
index d20a8b7..5afc0df 100644
--- a/content/browser/devtools/devtools_agent_host_impl.h
+++ b/content/browser/devtools/devtools_agent_host_impl.h
@@ -17,53 +17,47 @@ class Message;
 
 namespace content {
 
+class BrowserContext;
+
 // Describes interface for managing devtools agents from the browser process.
 class CONTENT_EXPORT DevToolsAgentHostImpl : public DevToolsAgentHost {
  public:
-  class CONTENT_EXPORT CloseListener {
-   public:
-    virtual void AgentHostClosing(DevToolsAgentHostImpl*) = 0;
-   protected:
-    virtual ~CloseListener() {}
-  };
-
   // Informs the hosted agent that a client host has attached.
   virtual void Attach() = 0;
 
   // Informs the hosted agent that a client host has detached.
   virtual void Detach() = 0;
 
-  // Sends a message to the agent hosted by this object.
-  virtual void DispatchOnInspectorBackend(const std::string& message) = 0;
+  // Sends a message to the agent.
+  virtual void DispatchProtocolMessage(const std::string& message) = 0;
 
-  void set_close_listener(CloseListener* listener) {
-    close_listener_ = listener;
-  }
+  // Opens the inspector for this host.
+  void Inspect(BrowserContext* browser_context);
 
   // DevToolsAgentHost implementation.
+  virtual void AttachClient(DevToolsAgentHostClient* client) OVERRIDE;
+  virtual void DetachClient() OVERRIDE;
   virtual bool IsAttached() OVERRIDE;
-
   virtual void InspectElement(int x, int y) OVERRIDE;
-
   virtual std::string GetId() OVERRIDE;
-
   virtual WebContents* GetWebContents() OVERRIDE;
-
   virtual void DisconnectWebContents() OVERRIDE;
-
-  virtual void ConnectWebContents(WebContents* rvh) OVERRIDE;
-
+  virtual void ConnectWebContents(WebContents* wc) OVERRIDE;
   virtual bool IsWorker() const OVERRIDE;
 
  protected:
   DevToolsAgentHostImpl();
   virtual ~DevToolsAgentHostImpl();
 
-  void NotifyCloseListener();
+  void HostClosed();
+  void SendMessageToClient(const std::string& message);
+  static void NotifyCallbacks(DevToolsAgentHostImpl* agent_host, bool attached);
 
  private:
-  CloseListener* close_listener_;
+  friend class DevToolsAgentHost; // for static methods
+
   const std::string id_;
+  DevToolsAgentHostClient* client_;
 };
 
 }  // namespace content
diff --git a/content/browser/devtools/devtools_http_handler_impl.cc b/content/browser/devtools/devtools_http_handler_impl.cc
index d1b5b1e..72fe254 100644
--- a/content/browser/devtools/devtools_http_handler_impl.cc
+++ b/content/browser/devtools/devtools_http_handler_impl.cc
@@ -26,9 +26,7 @@
 #include "content/common/devtools_messages.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_http_handler_delegate.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/devtools_target.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/url_constants.h"
@@ -69,30 +67,37 @@ const char kTargetFaviconUrlField[] = "faviconUrl";
 const char kTargetWebSocketDebuggerUrlField[] = "webSocketDebuggerUrl";
 const char kTargetDevtoolsFrontendUrlField[] = "devtoolsFrontendUrl";
 
-// An internal implementation of DevToolsClientHost that delegates
-// messages sent for DevToolsClient to a DebuggerShell instance.
-class DevToolsClientHostImpl : public DevToolsClientHost {
+// An internal implementation of DevToolsAgentHostClient that delegates
+// messages sent to a DebuggerShell instance.
+class DevToolsAgentHostClientImpl : public DevToolsAgentHostClient {
  public:
-  DevToolsClientHostImpl(base::MessageLoop* message_loop,
-                         net::HttpServer* server,
-                         int connection_id)
+  DevToolsAgentHostClientImpl(base::MessageLoop* message_loop,
+                              net::HttpServer* server,
+                              int connection_id,
+                              DevToolsAgentHost* agent_host)
       : message_loop_(message_loop),
         server_(server),
         connection_id_(connection_id),
-        is_closed_(false),
-        detach_reason_("target_closed") {}
+        agent_host_(agent_host) {
+    agent_host_->AttachClient(this);
+  }
 
-  virtual ~DevToolsClientHostImpl() {}
+  virtual ~DevToolsAgentHostClientImpl() {
+    if (agent_host_)
+      agent_host_->DetachClient();
+  }
 
-  // DevToolsClientHost interface
-  virtual void InspectedContentsClosing() OVERRIDE {
-    if (is_closed_)
-      return;
-    is_closed_ = true;
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host,
+      bool replaced_with_another_client) OVERRIDE {
+    DCHECK(agent_host == agent_host_.get());
+    agent_host_ = NULL;
 
     base::DictionaryValue notification;
     notification.SetString(
-        devtools::Inspector::detached::kParamReason, detach_reason_);
+        devtools::Inspector::detached::kParamReason,
+        replaced_with_another_client ?
+            "replaced_with_devtools" : "target_closed");
     std::string response = DevToolsProtocol::CreateNotification(
         devtools::Inspector::detached::kName,
         notification.DeepCopy())->Serialize();
@@ -108,25 +113,27 @@ class DevToolsClientHostImpl : public DevToolsClientHost {
         base::Bind(&net::HttpServer::Close, server_, connection_id_));
   }
 
-  virtual void DispatchOnInspectorFrontend(const std::string& data) OVERRIDE {
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE {
+    DCHECK(agent_host == agent_host_.get());
     message_loop_->PostTask(
         FROM_HERE,
         base::Bind(&net::HttpServer::SendOverWebSocket,
                    server_,
                    connection_id_,
-                   data));
+                   message));
   }
 
-  virtual void ReplacedWithAnotherClient() OVERRIDE {
-    detach_reason_ = "replaced_with_devtools";
+  void OnMessage(const std::string& message) {
+    if (agent_host_)
+      agent_host_->DispatchProtocolMessage(message);
   }
 
  private:
   base::MessageLoop* message_loop_;
   net::HttpServer* server_;
   int connection_id_;
-  bool is_closed_;
-  std::string detach_reason_;
+  scoped_refptr<DevToolsAgentHost> agent_host_;
 };
 
 static bool TimeComparator(const DevToolsTarget* target1,
@@ -612,12 +619,9 @@ void DevToolsHttpHandlerImpl::OnWebSocketRequestUI(
     return;
   }
 
-  DevToolsClientHostImpl* client_host = new DevToolsClientHostImpl(
-      thread_->message_loop(), server_.get(), connection_id);
-  connection_to_client_host_ui_[connection_id] = client_host;
-
-  DevToolsManager::GetInstance()->
-      RegisterDevToolsClientHostFor(agent, client_host);
+  DevToolsAgentHostClientImpl * client_host = new DevToolsAgentHostClientImpl(
+      thread_->message_loop(), server_.get(), connection_id, agent);
+  connection_to_client_ui_[connection_id] = client_host;
 
   AcceptWebSocket(connection_id, request);
 }
@@ -625,24 +629,24 @@ void DevToolsHttpHandlerImpl::OnWebSocketRequestUI(
 void DevToolsHttpHandlerImpl::OnWebSocketMessageUI(
     int connection_id,
     const std::string& data) {
-  ConnectionToClientHostMap::iterator it =
-      connection_to_client_host_ui_.find(connection_id);
-  if (it == connection_to_client_host_ui_.end())
+  ConnectionToClientMap::iterator it =
+      connection_to_client_ui_.find(connection_id);
+  if (it == connection_to_client_ui_.end())
     return;
 
-  DevToolsManager* manager = DevToolsManager::GetInstance();
-  manager->DispatchOnInspectorBackend(it->second, data);
+  DevToolsAgentHostClientImpl* client =
+      static_cast<DevToolsAgentHostClientImpl*>(it->second);
+  client->OnMessage(data);
 }
 
 void DevToolsHttpHandlerImpl::OnCloseUI(int connection_id) {
-  ConnectionToClientHostMap::iterator it =
-      connection_to_client_host_ui_.find(connection_id);
-  if (it != connection_to_client_host_ui_.end()) {
-    DevToolsClientHostImpl* client_host =
-        static_cast<DevToolsClientHostImpl*>(it->second);
-    DevToolsManager::GetInstance()->ClientHostClosing(client_host);
-    delete client_host;
-    connection_to_client_host_ui_.erase(connection_id);
+  ConnectionToClientMap::iterator it =
+      connection_to_client_ui_.find(connection_id);
+  if (it != connection_to_client_ui_.end()) {
+    DevToolsAgentHostClientImpl* client =
+        static_cast<DevToolsAgentHostClientImpl*>(it->second);
+    delete client;
+    connection_to_client_ui_.erase(connection_id);
   }
 }
 
diff --git a/content/browser/devtools/devtools_http_handler_impl.h b/content/browser/devtools/devtools_http_handler_impl.h
index 0d08d98..e9cee0b 100644
--- a/content/browser/devtools/devtools_http_handler_impl.h
+++ b/content/browser/devtools/devtools_http_handler_impl.h
@@ -13,6 +13,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/common/content_export.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/devtools_http_handler.h"
 #include "content/public/browser/devtools_http_handler_delegate.h"
 #include "net/http/http_status_code.h"
@@ -33,7 +34,6 @@ class URLRequestContextGetter;
 namespace content {
 
 class DevToolsBrowserTarget;
-class DevToolsClientHost;
 
 class DevToolsHttpHandlerImpl
     : public DevToolsHttpHandler,
@@ -119,8 +119,8 @@ class DevToolsHttpHandlerImpl
   std::string frontend_url_;
   scoped_ptr<const net::StreamListenSocketFactory> socket_factory_;
   scoped_refptr<net::HttpServer> server_;
-  typedef std::map<int, DevToolsClientHost*> ConnectionToClientHostMap;
-  ConnectionToClientHostMap connection_to_client_host_ui_;
+  typedef std::map<int, DevToolsAgentHostClient*> ConnectionToClientMap;
+  ConnectionToClientMap connection_to_client_ui_;
   scoped_ptr<DevToolsHttpHandlerDelegate> delegate_;
   base::FilePath active_port_output_directory_;
   typedef std::map<std::string, DevToolsTarget*> TargetMap;
diff --git a/content/browser/devtools/devtools_manager_impl.cc b/content/browser/devtools/devtools_manager_impl.cc
index 3aafd1c..4f40e80ba 100644
--- a/content/browser/devtools/devtools_manager_impl.cc
+++ b/content/browser/devtools/devtools_manager_impl.cc
@@ -4,199 +4,48 @@
 
 #include "content/browser/devtools/devtools_manager_impl.h"
 
-#include <vector>
-
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "content/browser/devtools/devtools_netlog_observer.h"
-#include "content/browser/devtools/render_view_devtools_agent_host.h"
-#include "content/browser/renderer_host/render_view_host_impl.h"
-#include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
-#include "content/public/browser/devtools_client_host.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/devtools_manager_delegate.h"
 
 namespace content {
 
 // static
-DevToolsManager* DevToolsManager::GetInstance() {
-  return DevToolsManagerImpl::GetInstance();
-}
-
-// static
 DevToolsManagerImpl* DevToolsManagerImpl::GetInstance() {
   return Singleton<DevToolsManagerImpl>::get();
 }
 
 DevToolsManagerImpl::DevToolsManagerImpl()
-    : delegate_(GetContentClient()->browser()->GetDevToolsManagerDelegate()) {
+    : delegate_(GetContentClient()->browser()->GetDevToolsManagerDelegate()),
+      client_count_(0) {
 }
 
 DevToolsManagerImpl::~DevToolsManagerImpl() {
-  DCHECK(agent_to_client_host_.empty());
-  DCHECK(client_to_agent_host_.empty());
-}
-
-void DevToolsManagerImpl::Inspect(BrowserContext* browser_context,
-                                  DevToolsAgentHost* agent_host) {
-  if (delegate_)
-    delegate_->Inspect(browser_context, agent_host);
-}
-
-DevToolsClientHost* DevToolsManagerImpl::GetDevToolsClientHostFor(
-    DevToolsAgentHostImpl* agent_host_impl) {
-  AgentToClientHostMap::iterator it =
-      agent_to_client_host_.find(agent_host_impl);
-  if (it != agent_to_client_host_.end())
-    return it->second;
-  return NULL;
-}
-
-DevToolsAgentHost* DevToolsManagerImpl::GetDevToolsAgentHostFor(
-    DevToolsClientHost* client_host) {
-  ClientToAgentHostMap::iterator it = client_to_agent_host_.find(client_host);
-  if (it != client_to_agent_host_.end())
-    return it->second.get();
-  return NULL;
+  DCHECK(!client_count_);
 }
 
-void DevToolsManagerImpl::RegisterDevToolsClientHostFor(
-    DevToolsAgentHost* agent_host,
-    DevToolsClientHost* client_host) {
-  DevToolsAgentHostImpl* agent_host_impl =
-      static_cast<DevToolsAgentHostImpl*>(agent_host);
-  DevToolsClientHost* old_client_host =
-      GetDevToolsClientHostFor(agent_host_impl);
-  if (old_client_host) {
-    old_client_host->ReplacedWithAnotherClient();
-    UnregisterDevToolsClientHostFor(agent_host_impl);
-  }
-  BindClientHost(agent_host_impl, client_host);
-  agent_host_impl->Attach();
-}
-
-bool DevToolsManagerImpl::DispatchOnInspectorBackend(
-    DevToolsClientHost* from,
-    const std::string& message) {
-  DevToolsAgentHost* agent_host = GetDevToolsAgentHostFor(from);
-  if (!agent_host)
-    return false;
-  DevToolsAgentHostImpl* agent_host_impl =
-      static_cast<DevToolsAgentHostImpl*>(agent_host);
-  agent_host_impl->DispatchOnInspectorBackend(message);
-  return true;
-}
-
-void DevToolsManagerImpl::DispatchOnInspectorFrontend(
-    DevToolsAgentHost* agent_host,
-    const std::string& message) {
-  DevToolsAgentHostImpl* agent_host_impl =
-      static_cast<DevToolsAgentHostImpl*>(agent_host);
-  DevToolsClientHost* client_host = GetDevToolsClientHostFor(agent_host_impl);
-  if (!client_host) {
-    // Client window was closed while there were messages
-    // being sent to it.
-    return;
-  }
-  client_host->DispatchOnInspectorFrontend(message);
-}
-
-void DevToolsManagerImpl::ClientHostClosing(DevToolsClientHost* client_host) {
-  DevToolsAgentHost* agent_host = GetDevToolsAgentHostFor(client_host);
-  if (!agent_host)
-    return;
-  DevToolsAgentHostImpl* agent_host_impl =
-      static_cast<DevToolsAgentHostImpl*>(agent_host);
-  UnbindClientHost(agent_host_impl, client_host);
-}
-
-void DevToolsManagerImpl::AgentHostClosing(DevToolsAgentHostImpl* agent_host) {
-  UnregisterDevToolsClientHostFor(agent_host);
-}
-
-void DevToolsManagerImpl::UnregisterDevToolsClientHostFor(
-    DevToolsAgentHostImpl* agent_host_impl) {
-  DevToolsClientHost* client_host = GetDevToolsClientHostFor(agent_host_impl);
-  if (!client_host)
-    return;
-  UnbindClientHost(agent_host_impl, client_host);
-  client_host->InspectedContentsClosing();
-}
-
-void DevToolsManagerImpl::BindClientHost(
-    DevToolsAgentHostImpl* agent_host,
-    DevToolsClientHost* client_host) {
-  DCHECK(agent_to_client_host_.find(agent_host) ==
-      agent_to_client_host_.end());
-  DCHECK(client_to_agent_host_.find(client_host) ==
-      client_to_agent_host_.end());
-
-  if (client_to_agent_host_.empty()) {
+void DevToolsManagerImpl::OnClientAttached() {
+  if (!client_count_) {
     BrowserThread::PostTask(
         BrowserThread::IO,
         FROM_HERE,
         base::Bind(&DevToolsNetLogObserver::Attach));
   }
-  agent_to_client_host_[agent_host] = client_host;
-  client_to_agent_host_[client_host] = agent_host;
-  agent_host->set_close_listener(this);
+  client_count_++;
 }
 
-void DevToolsManagerImpl::UnbindClientHost(DevToolsAgentHostImpl* agent_host,
-                                           DevToolsClientHost* client_host) {
-  DCHECK(agent_host);
-  scoped_refptr<DevToolsAgentHostImpl> protect(agent_host);
-  DCHECK(agent_to_client_host_.find(agent_host)->second ==
-      client_host);
-  DCHECK(client_to_agent_host_.find(client_host)->second.get() == agent_host);
-  agent_host->set_close_listener(NULL);
-
-  agent_to_client_host_.erase(agent_host);
-  client_to_agent_host_.erase(client_host);
-
-  if (client_to_agent_host_.empty()) {
+void DevToolsManagerImpl::OnClientDetached() {
+  client_count_--;
+  if (!client_count_) {
     BrowserThread::PostTask(
         BrowserThread::IO,
         FROM_HERE,
         base::Bind(&DevToolsNetLogObserver::Detach));
   }
-  // Lazy agent hosts can be deleted from within detach.
-  // Do not access agent_host below this line.
-  agent_host->Detach();
-}
-
-void DevToolsManagerImpl::CloseAllClientHosts() {
-  std::vector<DevToolsAgentHostImpl*> agents;
-  for (AgentToClientHostMap::iterator it =
-           agent_to_client_host_.begin();
-       it != agent_to_client_host_.end(); ++it) {
-    agents.push_back(it->first);
-  }
-  for (std::vector<DevToolsAgentHostImpl*>::iterator it = agents.begin();
-       it != agents.end(); ++it) {
-    UnregisterDevToolsClientHostFor(*it);
-  }
-}
-
-void DevToolsManagerImpl::AddAgentStateCallback(const Callback& callback) {
-  callbacks_.push_back(&callback);
-}
-
-void DevToolsManagerImpl::RemoveAgentStateCallback(const Callback& callback) {
-  CallbackContainer::iterator it =
-      std::find(callbacks_.begin(), callbacks_.end(), &callback);
-  DCHECK(it != callbacks_.end());
-  callbacks_.erase(it);
-}
-
-void DevToolsManagerImpl::NotifyObservers(DevToolsAgentHost* agent_host,
-                                          bool attached) {
-  CallbackContainer copy(callbacks_);
-  if (delegate_)
-    delegate_->DevToolsAgentStateChanged(agent_host, attached);
-  for (CallbackContainer::iterator it = copy.begin(); it != copy.end(); ++it)
-     (*it)->Run(agent_host, attached);
 }
 
 }  // namespace content
diff --git a/content/browser/devtools/devtools_manager_impl.h b/content/browser/devtools/devtools_manager_impl.h
index 19b6918..c5ceb2a 100644
--- a/content/browser/devtools/devtools_manager_impl.h
+++ b/content/browser/devtools/devtools_manager_impl.h
@@ -11,32 +11,14 @@
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
-#include "content/browser/devtools/devtools_agent_host_impl.h"
-#include "content/common/content_export.h"
-#include "content/public/browser/devtools_client_host.h"
-#include "content/public/browser/devtools_manager.h"
-
-class GURL;
-
-namespace IPC {
-class Message;
-}
 
 namespace content {
 
-class BrowserContext;
 class DevToolsManagerDelegate;
-class RenderViewHost;
 
-// This class is a singleton that manages DevToolsClientHost instances and
-// routes messages between developer tools clients and agents.
-//
-// Methods below that accept inspected RenderViewHost as a parameter are
-// just convenience methods that call corresponding methods accepting
-// DevToolAgentHost.
-class CONTENT_EXPORT DevToolsManagerImpl
-    : public DevToolsAgentHostImpl::CloseListener,
-      public DevToolsManager {
+// This class is a singleton that manage global DevTools state for the whole
+// browser.
+class DevToolsManagerImpl {
  public:
   // Returns single instance of this class. The instance is destroyed on the
   // browser main loop exit so this method MUST NOT be called after that point.
@@ -45,65 +27,15 @@ class CONTENT_EXPORT DevToolsManagerImpl
   DevToolsManagerImpl();
   virtual ~DevToolsManagerImpl();
 
-  // Opens the inspector for |agent_host|.
-  void Inspect(BrowserContext* browser_context, DevToolsAgentHost* agent_host);
-
-  void DispatchOnInspectorFrontend(DevToolsAgentHost* agent_host,
-                                   const std::string& message);
-
   DevToolsManagerDelegate* delegate() const { return delegate_.get(); }
-
-  // DevToolsManager implementation
-  virtual bool DispatchOnInspectorBackend(DevToolsClientHost* from,
-                                          const std::string& message) OVERRIDE;
-  virtual void CloseAllClientHosts() OVERRIDE;
-  virtual DevToolsAgentHost* GetDevToolsAgentHostFor(
-      DevToolsClientHost* client_host) OVERRIDE;
-  virtual void RegisterDevToolsClientHostFor(
-      DevToolsAgentHost* agent_host,
-      DevToolsClientHost* client_host) OVERRIDE;
-  virtual void ClientHostClosing(DevToolsClientHost* host) OVERRIDE;
-  virtual void AddAgentStateCallback(const Callback& callback) OVERRIDE;
-  virtual void RemoveAgentStateCallback(const Callback& callback) OVERRIDE;
+  void OnClientAttached();
+  void OnClientDetached();
 
  private:
-  friend class DevToolsAgentHostImpl;
-  friend class RenderViewDevToolsAgentHost;
   friend struct DefaultSingletonTraits<DevToolsManagerImpl>;
 
-  // DevToolsAgentHost::CloseListener implementation.
-  virtual void AgentHostClosing(DevToolsAgentHostImpl* host) OVERRIDE;
-
-  void BindClientHost(DevToolsAgentHostImpl* agent_host,
-                      DevToolsClientHost* client_host);
-  void UnbindClientHost(DevToolsAgentHostImpl* agent_host,
-                        DevToolsClientHost* client_host);
-
-  DevToolsClientHost* GetDevToolsClientHostFor(
-      DevToolsAgentHostImpl* agent_host);
-
-  void UnregisterDevToolsClientHostFor(DevToolsAgentHostImpl* agent_host);
-
-  void NotifyObservers(DevToolsAgentHost* agent_host, bool attached);
-
-  // These two maps are for tracking dependencies between inspected contents and
-  // their DevToolsClientHosts. They are useful for routing devtools messages
-  // and allow us to have at most one devtools client host per contents.
-  //
-  // DevToolsManagerImpl starts listening to DevToolsClientHosts when they are
-  // put into these maps and removes them when they are closing.
-  typedef std::map<DevToolsAgentHostImpl*, DevToolsClientHost*>
-      AgentToClientHostMap;
-  AgentToClientHostMap agent_to_client_host_;
-
-  typedef std::map<DevToolsClientHost*, scoped_refptr<DevToolsAgentHostImpl> >
-      ClientToAgentHostMap;
-  ClientToAgentHostMap client_to_agent_host_;
-
-  typedef std::vector<const Callback*> CallbackContainer;
-  CallbackContainer callbacks_;
-
   scoped_ptr<DevToolsManagerDelegate> delegate_;
+  int client_count_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsManagerImpl);
 };
diff --git a/content/browser/devtools/devtools_manager_unittest.cc b/content/browser/devtools/devtools_manager_unittest.cc
index 79b7654..588e530 100644
--- a/content/browser/devtools/devtools_manager_unittest.cc
+++ b/content/browser/devtools/devtools_manager_unittest.cc
@@ -10,7 +10,6 @@
 #include "content/common/view_messages.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_external_agent_proxy.h"
 #include "content/public/browser/devtools_external_agent_proxy_delegate.h"
 #include "content/public/browser/web_contents_delegate.h"
@@ -24,7 +23,7 @@ using base::TimeDelta;
 namespace content {
 namespace {
 
-class TestDevToolsClientHost : public DevToolsClientHost {
+class TestDevToolsClientHost : public DevToolsAgentHostClient {
  public:
   TestDevToolsClientHost()
       : last_sent_message(NULL),
@@ -35,24 +34,30 @@ class TestDevToolsClientHost : public DevToolsClientHost {
     EXPECT_TRUE(closed_);
   }
 
-  virtual void Close(DevToolsManager* manager) {
+  void Close() {
     EXPECT_FALSE(closed_);
     close_counter++;
-    manager->ClientHostClosing(this);
+    agent_host_->DetachClient();
     closed_ = true;
   }
-  virtual void InspectedContentsClosing() OVERRIDE {
+
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host, bool replaced) OVERRIDE {
     FAIL();
   }
 
-  virtual void DispatchOnInspectorFrontend(
-      const std::string& message) OVERRIDE {
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE {
     last_sent_message = &message;
   }
 
-  virtual void ReplacedWithAnotherClient() OVERRIDE {
+  void InspectAgentHost(DevToolsAgentHost* agent_host) {
+    agent_host_ = agent_host;
+    agent_host_->AttachClient(this);
   }
 
+  DevToolsAgentHost* agent_host() { return agent_host_.get(); }
+
   static void ResetCounters() {
     close_counter = 0;
   }
@@ -63,6 +68,7 @@ class TestDevToolsClientHost : public DevToolsClientHost {
 
  private:
   bool closed_;
+  scoped_refptr<DevToolsAgentHost> agent_host_;
 
   DISALLOW_COPY_AND_ASSIGN(TestDevToolsClientHost);
 };
@@ -98,42 +104,21 @@ class DevToolsManagerTest : public RenderViewHostImplTestHarness {
 };
 
 TEST_F(DevToolsManagerTest, OpenAndManuallyCloseDevToolsClientHost) {
-  DevToolsManager* manager = DevToolsManager::GetInstance();
-
   scoped_refptr<DevToolsAgentHost> agent(
       DevToolsAgentHost::GetOrCreateFor(web_contents()));
   EXPECT_FALSE(agent->IsAttached());
 
   TestDevToolsClientHost client_host;
-  manager->RegisterDevToolsClientHostFor(agent.get(), &client_host);
+  client_host.InspectAgentHost(agent.get());
   // Test that the connection is established.
   EXPECT_TRUE(agent->IsAttached());
-  EXPECT_EQ(agent, manager->GetDevToolsAgentHostFor(&client_host));
   EXPECT_EQ(0, TestDevToolsClientHost::close_counter);
 
-  client_host.Close(manager);
+  client_host.Close();
   EXPECT_EQ(1, TestDevToolsClientHost::close_counter);
   EXPECT_FALSE(agent->IsAttached());
 }
 
-TEST_F(DevToolsManagerTest, ForwardMessageToClient) {
-  DevToolsManagerImpl* manager = DevToolsManagerImpl::GetInstance();
-
-  TestDevToolsClientHost client_host;
-  scoped_refptr<DevToolsAgentHost> agent_host(
-      DevToolsAgentHost::GetOrCreateFor(web_contents()));
-  manager->RegisterDevToolsClientHostFor(agent_host.get(), &client_host);
-  EXPECT_EQ(0, TestDevToolsClientHost::close_counter);
-
-  std::string m = "test message";
-  agent_host = DevToolsAgentHost::GetOrCreateFor(web_contents());
-  manager->DispatchOnInspectorFrontend(agent_host.get(), m);
-  EXPECT_TRUE(&m == client_host.last_sent_message);
-
-  client_host.Close(manager);
-  EXPECT_EQ(1, TestDevToolsClientHost::close_counter);
-}
-
 TEST_F(DevToolsManagerTest, NoUnresponsiveDialogInInspectedContents) {
   TestRenderViewHost* inspected_rvh = test_rvh();
   inspected_rvh->set_render_view_created(true);
@@ -144,8 +129,7 @@ TEST_F(DevToolsManagerTest, NoUnresponsiveDialogInInspectedContents) {
   TestDevToolsClientHost client_host;
   scoped_refptr<DevToolsAgentHost> agent_host(DevToolsAgentHost::GetOrCreateFor(
       WebContents::FromRenderViewHost(inspected_rvh)));
-  DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-      agent_host.get(), &client_host);
+  client_host.InspectAgentHost(agent_host.get());
 
   // Start with a short timeout.
   inspected_rvh->StartHangMonitorTimeout(TimeDelta::FromMilliseconds(10));
@@ -158,7 +142,7 @@ TEST_F(DevToolsManagerTest, NoUnresponsiveDialogInInspectedContents) {
   EXPECT_FALSE(delegate.renderer_unresponsive_received());
 
   // Now close devtools and check that the notification is delivered.
-  client_host.Close(DevToolsManager::GetInstance());
+  client_host.Close();
   // Start with a short timeout.
   inspected_rvh->StartHangMonitorTimeout(TimeDelta::FromMilliseconds(10));
   // Wait long enough for first timeout and see if it fired.
@@ -181,26 +165,25 @@ TEST_F(DevToolsManagerTest, ReattachOnCancelPendingNavigation) {
   EXPECT_FALSE(contents()->cross_navigation_pending());
 
   TestDevToolsClientHost client_host;
-  DevToolsManager* devtools_manager = DevToolsManager::GetInstance();
-  devtools_manager->RegisterDevToolsClientHostFor(
-      DevToolsAgentHost::GetOrCreateFor(web_contents()).get(), &client_host);
+  client_host.InspectAgentHost(
+      DevToolsAgentHost::GetOrCreateFor(web_contents()).get());
 
   // Navigate to new site which should get a new RenderViewHost.
   const GURL url2("http://www.yahoo.com");
   controller().LoadURL(
       url2, Referrer(), PAGE_TRANSITION_TYPED, std::string());
   EXPECT_TRUE(contents()->cross_navigation_pending());
-  EXPECT_EQ(devtools_manager->GetDevToolsAgentHostFor(&client_host),
-            DevToolsAgentHost::GetOrCreateFor(web_contents()));
+  EXPECT_EQ(client_host.agent_host(),
+      DevToolsAgentHost::GetOrCreateFor(web_contents()));
 
   // Interrupt pending navigation and navigate back to the original site.
   controller().LoadURL(
       url, Referrer(), PAGE_TRANSITION_TYPED, std::string());
   contents()->TestDidNavigate(rvh(), 1, url, PAGE_TRANSITION_TYPED);
   EXPECT_FALSE(contents()->cross_navigation_pending());
-  EXPECT_EQ(devtools_manager->GetDevToolsAgentHostFor(&client_host),
+  EXPECT_EQ(client_host.agent_host(),
             DevToolsAgentHost::GetOrCreateFor(web_contents()));
-  client_host.Close(DevToolsManager::GetInstance());
+  client_host.Close();
 }
 
 class TestExternalAgentDelegate: public DevToolsExternalAgentProxyDelegate {
@@ -245,16 +228,13 @@ TEST_F(DevToolsManagerTest, TestExternalProxy) {
       DevToolsAgentHost::Create(delegate);
   EXPECT_EQ(agent_host, DevToolsAgentHost::GetForId(agent_host->GetId()));
 
-  DevToolsManager* manager = DevToolsManager::GetInstance();
-
   TestDevToolsClientHost client_host;
-  manager->RegisterDevToolsClientHostFor(agent_host.get(), &client_host);
-
-  manager->DispatchOnInspectorBackend(&client_host, "message1");
-  manager->DispatchOnInspectorBackend(&client_host, "message2");
-  manager->DispatchOnInspectorBackend(&client_host, "message2");
+  client_host.InspectAgentHost(agent_host.get());
+  agent_host->DispatchProtocolMessage("message1");
+  agent_host->DispatchProtocolMessage("message2");
+  agent_host->DispatchProtocolMessage("message2");
 
-  client_host.Close(manager);
+  client_host.Close();
 }
 
 }  // namespace content
diff --git a/content/browser/devtools/embedded_worker_devtools_agent_host.cc b/content/browser/devtools/embedded_worker_devtools_agent_host.cc
index 9f60400..8a7a948 100644
--- a/content/browser/devtools/embedded_worker_devtools_agent_host.cc
+++ b/content/browser/devtools/embedded_worker_devtools_agent_host.cc
@@ -83,7 +83,7 @@ bool EmbeddedWorkerDevToolsAgentHost::OnMessageReceived(
 void EmbeddedWorkerDevToolsAgentHost::WorkerContextStarted() {
   if (state_ == WORKER_PAUSED_FOR_DEBUG_ON_START) {
     RenderProcessHost* rph = RenderProcessHost::FromID(worker_id_.first);
-    DevToolsManagerImpl::GetInstance()->Inspect(rph->GetBrowserContext(), this);
+    Inspect(rph->GetBrowserContext());
   } else if (state_ == WORKER_PAUSED_FOR_REATTACH) {
     DCHECK(IsAttached());
     state_ = WORKER_INSPECTED;
@@ -107,8 +107,7 @@ void EmbeddedWorkerDevToolsAgentHost::WorkerDestroyed() {
     std::string notification =
         DevToolsProtocol::CreateNotification(
             devtools::Worker::disconnectedFromWorker::kName, NULL)->Serialize();
-    DevToolsManagerImpl::GetInstance()->DispatchOnInspectorFrontend(
-        this, notification);
+    SendMessageToClient(notification);
     DetachFromWorker();
   }
   state_ = WORKER_TERMINATED;
@@ -147,8 +146,7 @@ void EmbeddedWorkerDevToolsAgentHost::WorkerCreated() {
 
 void EmbeddedWorkerDevToolsAgentHost::OnDispatchOnInspectorFrontend(
     const std::string& message) {
-  DevToolsManagerImpl::GetInstance()->DispatchOnInspectorFrontend(
-      this, message);
+  SendMessageToClient(message);
 }
 
 void EmbeddedWorkerDevToolsAgentHost::OnSaveAgentRuntimeState(
diff --git a/content/browser/devtools/embedded_worker_devtools_manager.cc b/content/browser/devtools/embedded_worker_devtools_manager.cc
index cf4c831..2ba644f 100644
--- a/content/browser/devtools/embedded_worker_devtools_manager.cc
+++ b/content/browser/devtools/embedded_worker_devtools_manager.cc
@@ -52,7 +52,8 @@ EmbeddedWorkerDevToolsManager* EmbeddedWorkerDevToolsManager::GetInstance() {
   return Singleton<EmbeddedWorkerDevToolsManager>::get();
 }
 
-DevToolsAgentHost* EmbeddedWorkerDevToolsManager::GetDevToolsAgentHostForWorker(
+DevToolsAgentHostImpl*
+EmbeddedWorkerDevToolsManager::GetDevToolsAgentHostForWorker(
     int worker_process_id,
     int worker_route_id) {
   AgentHostMap::iterator it = workers_.find(
@@ -60,7 +61,7 @@ DevToolsAgentHost* EmbeddedWorkerDevToolsManager::GetDevToolsAgentHostForWorker(
   return it == workers_.end() ? NULL : it->second;
 }
 
-DevToolsAgentHost*
+DevToolsAgentHostImpl*
 EmbeddedWorkerDevToolsManager::GetDevToolsAgentHostForServiceWorker(
     const ServiceWorkerIdentifier& service_worker_id) {
   AgentHostMap::iterator it =
diff --git a/content/browser/devtools/embedded_worker_devtools_manager.h b/content/browser/devtools/embedded_worker_devtools_manager.h
index 4fcfb9b..0e00499 100644
--- a/content/browser/devtools/embedded_worker_devtools_manager.h
+++ b/content/browser/devtools/embedded_worker_devtools_manager.h
@@ -17,7 +17,7 @@
 
 namespace content {
 
-class DevToolsAgentHost;
+class DevToolsAgentHostImpl;
 class EmbeddedWorkerDevToolsAgentHost;
 class ServiceWorkerContextCore;
 
@@ -46,9 +46,9 @@ class CONTENT_EXPORT EmbeddedWorkerDevToolsManager {
   // Returns the EmbeddedWorkerDevToolsManager singleton.
   static EmbeddedWorkerDevToolsManager* GetInstance();
 
-  DevToolsAgentHost* GetDevToolsAgentHostForWorker(int worker_process_id,
+  DevToolsAgentHostImpl* GetDevToolsAgentHostForWorker(int worker_process_id,
                                                    int worker_route_id);
-  DevToolsAgentHost* GetDevToolsAgentHostForServiceWorker(
+  DevToolsAgentHostImpl* GetDevToolsAgentHostForServiceWorker(
       const ServiceWorkerIdentifier& service_worker_id);
 
   // Returns true when the worker must be paused on start because a DevTool
diff --git a/content/browser/devtools/embedded_worker_devtools_manager_unittest.cc b/content/browser/devtools/embedded_worker_devtools_manager_unittest.cc
index 347b6f3..5910b05 100644
--- a/content/browser/devtools/embedded_worker_devtools_manager_unittest.cc
+++ b/content/browser/devtools/embedded_worker_devtools_manager_unittest.cc
@@ -8,28 +8,34 @@
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "content/browser/browser_thread_impl.h"
-#include "content/browser/devtools/devtools_manager_impl.h"
+#include "content/browser/devtools/devtools_agent_host_impl.h"
 #include "content/browser/devtools/embedded_worker_devtools_agent_host.h"
 #include "content/browser/shared_worker/shared_worker_instance.h"
 #include "content/browser/shared_worker/worker_storage_partition.h"
-#include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/test/test_browser_context.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace content {
 namespace {
 
-class TestDevToolsClientHost : public DevToolsClientHost {
+class TestDevToolsClientHost : public DevToolsAgentHostClient {
  public:
   TestDevToolsClientHost() {}
   virtual ~TestDevToolsClientHost() {}
-  virtual void DispatchOnInspectorFrontend(
-      const std::string& message) OVERRIDE {}
-  virtual void InspectedContentsClosing() OVERRIDE {}
-  virtual void ReplacedWithAnotherClient() OVERRIDE {}
-
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE {}
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host, bool replaced) OVERRIDE {}
+
+  void InspectAgentHost(DevToolsAgentHost* agent_host) {
+    if (agent_host_)
+      agent_host_->DetachClient();
+    agent_host_ = agent_host;
+    if (agent_host_)
+      agent_host_->AttachClient(this);
+  }
  private:
+  scoped_refptr<DevToolsAgentHost> agent_host_;
   DISALLOW_COPY_AND_ASSIGN(TestDevToolsClientHost);
 };
 }
@@ -81,16 +87,6 @@ class EmbeddedWorkerDevToolsManagerTest : public testing::Test {
     EXPECT_EQ(size, manager_->workers_.size());
   }
 
-  void RegisterDevToolsClientHostFor(DevToolsAgentHost* agent_host,
-                                     DevToolsClientHost* client_host) {
-    DevToolsManagerImpl::GetInstance()->RegisterDevToolsClientHostFor(
-        agent_host, client_host);
-  }
-
-  void ClientHostClosing(DevToolsClientHost* client_host) {
-    DevToolsManagerImpl::GetInstance()->ClientHostClosing(client_host);
-  }
-
   base::MessageLoopForIO message_loop_;
   BrowserThreadImpl ui_thread_;
   scoped_ptr<TestBrowserContext> browser_context_;
@@ -100,7 +96,7 @@ class EmbeddedWorkerDevToolsManagerTest : public testing::Test {
 };
 
 TEST_F(EmbeddedWorkerDevToolsManagerTest, BasicTest) {
-  scoped_refptr<DevToolsAgentHost> agent_host;
+  scoped_refptr<DevToolsAgentHostImpl> agent_host;
 
   SharedWorkerInstance instance1(GURL("http://example.com/w.js"),
                                  base::string16(),
@@ -182,8 +178,8 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, BasicTest) {
 }
 
 TEST_F(EmbeddedWorkerDevToolsManagerTest, AttachTest) {
-  scoped_refptr<DevToolsAgentHost> agent_host1;
-  scoped_refptr<DevToolsAgentHost> agent_host2;
+  scoped_refptr<DevToolsAgentHostImpl> agent_host1;
+  scoped_refptr<DevToolsAgentHostImpl> agent_host2;
 
   SharedWorkerInstance instance1(GURL("http://example.com/w1.js"),
                                  base::string16(),
@@ -207,7 +203,7 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, AttachTest) {
   EXPECT_TRUE(agent_host1.get());
   CheckWorkerState(2, 1, WorkerState::WORKER_UNINSPECTED);
   EXPECT_EQ(agent_host1.get(), manager_->GetDevToolsAgentHostForWorker(2, 1));
-  RegisterDevToolsClientHostFor(agent_host1.get(), client_host1.get());
+  client_host1->InspectAgentHost(agent_host1.get());
   CheckWorkerState(2, 1, WorkerState::WORKER_INSPECTED);
   manager_->WorkerContextStarted(2, 1);
   CheckWorkerState(2, 1, WorkerState::WORKER_INSPECTED);
@@ -226,7 +222,7 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, AttachTest) {
   EXPECT_NE(agent_host1.get(), agent_host2.get());
   EXPECT_EQ(agent_host2.get(), manager_->GetDevToolsAgentHostForWorker(2, 2));
   CheckWorkerState(2, 2, WorkerState::WORKER_UNINSPECTED);
-  RegisterDevToolsClientHostFor(agent_host2.get(), client_host2.get());
+  client_host2->InspectAgentHost(agent_host2);
   CheckWorkerState(2, 2, WorkerState::WORKER_INSPECTED);
   manager_->WorkerDestroyed(2, 2);
   CheckWorkerState(2, 2, WorkerState::WORKER_TERMINATED);
@@ -240,7 +236,7 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, AttachTest) {
   EXPECT_EQ(agent_host1.get(), manager_->GetDevToolsAgentHostForWorker(2, 3));
   manager_->WorkerContextStarted(2, 3);
   CheckWorkerState(2, 3, WorkerState::WORKER_INSPECTED);
-  ClientHostClosing(client_host1.get());
+  client_host1->InspectAgentHost(NULL);
   manager_->WorkerDestroyed(2, 3);
   CheckWorkerState(2, 3, WorkerState::WORKER_TERMINATED);
   agent_host1 = NULL;
@@ -261,7 +257,7 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, AttachTest) {
   CheckWorkerNotExist(2, 2);
   CheckWorkerState(2, 5, WorkerState::WORKER_PAUSED_FOR_REATTACH);
   EXPECT_EQ(agent_host2.get(), manager_->GetDevToolsAgentHostForWorker(2, 5));
-  ClientHostClosing(client_host2.get());
+  client_host2->InspectAgentHost(NULL);
   CheckWorkerCount(1);
   agent_host2 = NULL;
   CheckWorkerCount(1);
@@ -284,12 +280,12 @@ TEST_F(EmbeddedWorkerDevToolsManagerTest, ReattachTest) {
       manager_->GetDevToolsAgentHostForWorker(3, 1));
   EXPECT_TRUE(agent_host.get());
   CheckWorkerState(3, 1, WorkerState::WORKER_UNINSPECTED);
-  RegisterDevToolsClientHostFor(agent_host.get(), client_host.get());
+  client_host->InspectAgentHost(agent_host.get());
   CheckWorkerState(3, 1, WorkerState::WORKER_INSPECTED);
   manager_->WorkerDestroyed(3, 1);
   CheckWorkerState(3, 1, WorkerState::WORKER_TERMINATED);
   // ClientHostClosing -> Re-created -> release agent_host -> Destroyed
-  ClientHostClosing(client_host.get());
+  client_host->InspectAgentHost(NULL);
   CheckWorkerState(3, 1, WorkerState::WORKER_TERMINATED);
   manager_->SharedWorkerCreated(3, 2, instance);
   CheckWorkerState(3, 2, WorkerState::WORKER_UNINSPECTED);
diff --git a/content/browser/devtools/forwarding_agent_host.cc b/content/browser/devtools/forwarding_agent_host.cc
index f1524e1..5267ae1 100644
--- a/content/browser/devtools/forwarding_agent_host.cc
+++ b/content/browser/devtools/forwarding_agent_host.cc
@@ -17,12 +17,11 @@ ForwardingAgentHost::~ForwardingAgentHost() {
 }
 
 void ForwardingAgentHost::DispatchOnClientHost(const std::string& message) {
-  DevToolsManagerImpl::GetInstance()->DispatchOnInspectorFrontend(
-      this, message);
+  SendMessageToClient(message);
 }
 
 void ForwardingAgentHost::ConnectionClosed() {
-  NotifyCloseListener();
+  HostClosed();
 }
 
 void ForwardingAgentHost::Attach() {
@@ -33,7 +32,7 @@ void ForwardingAgentHost::Detach() {
   delegate_->Detach();
 }
 
-void ForwardingAgentHost::DispatchOnInspectorBackend(
+void ForwardingAgentHost::DispatchProtocolMessage(
     const std::string& message) {
   delegate_->SendMessageToBackend(message);
 }
diff --git a/content/browser/devtools/forwarding_agent_host.h b/content/browser/devtools/forwarding_agent_host.h
index 81e4aed..93dabb4 100644
--- a/content/browser/devtools/forwarding_agent_host.h
+++ b/content/browser/devtools/forwarding_agent_host.h
@@ -29,7 +29,7 @@ class ForwardingAgentHost
   // DevToolsAgentHostImpl implementation.
   virtual void Attach() OVERRIDE;
   virtual void Detach() OVERRIDE;
-  virtual void DispatchOnInspectorBackend(const std::string& message) OVERRIDE;
+  virtual void DispatchProtocolMessage(const std::string& message) OVERRIDE;
 
   scoped_ptr<DevToolsExternalAgentProxyDelegate> delegate_;
 };
diff --git a/content/browser/devtools/ipc_devtools_agent_host.cc b/content/browser/devtools/ipc_devtools_agent_host.cc
index 294a679..18c362e 100644
--- a/content/browser/devtools/ipc_devtools_agent_host.cc
+++ b/content/browser/devtools/ipc_devtools_agent_host.cc
@@ -18,7 +18,7 @@ void IPCDevToolsAgentHost::Detach() {
   OnClientDetached();
 }
 
-void IPCDevToolsAgentHost::DispatchOnInspectorBackend(
+void IPCDevToolsAgentHost::DispatchProtocolMessage(
     const std::string& message) {
   SendMessageToAgent(new DevToolsAgentMsg_DispatchOnInspectorBackend(
       MSG_ROUTING_NONE, message));
diff --git a/content/browser/devtools/ipc_devtools_agent_host.h b/content/browser/devtools/ipc_devtools_agent_host.h
index 98c2794..496c2d9 100644
--- a/content/browser/devtools/ipc_devtools_agent_host.h
+++ b/content/browser/devtools/ipc_devtools_agent_host.h
@@ -18,7 +18,7 @@ class CONTENT_EXPORT IPCDevToolsAgentHost : public DevToolsAgentHostImpl {
   // DevToolsAgentHostImpl implementation.
   virtual void Attach() OVERRIDE;
   virtual void Detach() OVERRIDE;
-  virtual void DispatchOnInspectorBackend(const std::string& message) OVERRIDE;
+  virtual void DispatchProtocolMessage(const std::string& message) OVERRIDE;
   virtual void InspectElement(int x, int y) OVERRIDE;
 
  protected:
diff --git a/content/browser/devtools/render_view_devtools_agent_host.cc b/content/browser/devtools/render_view_devtools_agent_host.cc
index f0c9c8f..b16c2dc 100644
--- a/content/browser/devtools/render_view_devtools_agent_host.cc
+++ b/content/browser/devtools/render_view_devtools_agent_host.cc
@@ -127,7 +127,7 @@ WebContents* RenderViewDevToolsAgentHost::GetWebContents() {
   return web_contents();
 }
 
-void RenderViewDevToolsAgentHost::DispatchOnInspectorBackend(
+void RenderViewDevToolsAgentHost::DispatchProtocolMessage(
     const std::string& message) {
   std::string error_message;
 
@@ -161,7 +161,7 @@ void RenderViewDevToolsAgentHost::DispatchOnInspectorBackend(
     }
   }
 
-  IPCDevToolsAgentHost::DispatchOnInspectorBackend(message);
+  IPCDevToolsAgentHost::DispatchProtocolMessage(message);
 }
 
 void RenderViewDevToolsAgentHost::SendMessageToAgent(IPC::Message* msg) {
@@ -180,7 +180,7 @@ void RenderViewDevToolsAgentHost::OnClientAttached() {
   // TODO(kaznacheev): Move this call back to DevToolsManagerImpl when
   // extensions::ProcessManager no longer relies on this notification.
   if (!reattaching_)
-    DevToolsManagerImpl::GetInstance()->NotifyObservers(this, true);
+    DevToolsAgentHostImpl::NotifyCallbacks(this, true);
 }
 
 void RenderViewDevToolsAgentHost::InnerOnClientAttached() {
@@ -212,7 +212,7 @@ void RenderViewDevToolsAgentHost::OnClientDetached() {
   // TODO(kaznacheev): Move this call back to DevToolsManagerImpl when
   // extensions::ProcessManager no longer relies on this notification.
   if (!reattaching_)
-    DevToolsManagerImpl::GetInstance()->NotifyObservers(this, false);
+    DevToolsAgentHostImpl::NotifyCallbacks(this, false);
 }
 
 void RenderViewDevToolsAgentHost::ClientDetachedFromRenderer() {
@@ -286,7 +286,7 @@ void RenderViewDevToolsAgentHost::RenderViewDeleted(RenderViewHost* rvh) {
 
   DCHECK(render_view_host_);
   scoped_refptr<RenderViewDevToolsAgentHost> protect(this);
-  NotifyCloseListener();
+  HostClosed();
   ClearRenderViewHost();
   Release();
 }
@@ -385,8 +385,7 @@ void RenderViewDevToolsAgentHost::RenderViewCrashed() {
   scoped_refptr<DevToolsProtocol::Notification> notification =
       DevToolsProtocol::CreateNotification(
           devtools::Inspector::targetCrashed::kName, NULL);
-  DevToolsManagerImpl::GetInstance()->
-      DispatchOnInspectorFrontend(this, notification->Serialize());
+  SendMessageToClient(notification->Serialize());
 }
 
 bool RenderViewDevToolsAgentHost::DispatchIPCMessage(
@@ -447,8 +446,7 @@ void RenderViewDevToolsAgentHost::OnDispatchOnInspectorFrontend(
   if (notification) {
     tracing_handler_->HandleNotification(notification);
   }
-  DevToolsManagerImpl::GetInstance()->DispatchOnInspectorFrontend(
-      this, message);
+  SendMessageToClient(message);
 }
 
 }  // namespace content
diff --git a/content/browser/devtools/render_view_devtools_agent_host.h b/content/browser/devtools/render_view_devtools_agent_host.h
index b1f3e07..7de31fd 100644
--- a/content/browser/devtools/render_view_devtools_agent_host.h
+++ b/content/browser/devtools/render_view_devtools_agent_host.h
@@ -54,7 +54,7 @@ class CONTENT_EXPORT RenderViewDevToolsAgentHost
   virtual ~RenderViewDevToolsAgentHost();
 
   // IPCDevToolsAgentHost overrides.
-  virtual void DispatchOnInspectorBackend(const std::string& message) OVERRIDE;
+  virtual void DispatchProtocolMessage(const std::string& message) OVERRIDE;
   virtual void SendMessageToAgent(IPC::Message* msg) OVERRIDE;
   virtual void OnClientAttached() OVERRIDE;
   virtual void OnClientDetached() OVERRIDE;
diff --git a/content/browser/devtools/renderer_overrides_handler_browsertest.cc b/content/browser/devtools/renderer_overrides_handler_browsertest.cc
index a6cd973..48ae7c6 100644
--- a/content/browser/devtools/renderer_overrides_handler_browsertest.cc
+++ b/content/browser/devtools/renderer_overrides_handler_browsertest.cc
@@ -7,8 +7,6 @@
 #include "base/json/json_reader.h"
 #include "content/browser/devtools/devtools_protocol.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/content_browser_test.h"
@@ -20,12 +18,12 @@
 namespace content {
 
 class RendererOverridesHandlerTest : public ContentBrowserTest,
-                                     public DevToolsClientHost {
+                                     public DevToolsAgentHostClient {
  protected:
   void SendCommand(const std::string& method,
                    base::DictionaryValue* params) {
-    EXPECT_TRUE(DevToolsManager::GetInstance()->DispatchOnInspectorBackend(this,
-        DevToolsProtocol::CreateCommand(1, method, params)->Serialize()));
+    agent_host_->DispatchProtocolMessage(
+        DevToolsProtocol::CreateCommand(1, method, params)->Serialize());
     base::MessageLoop::current()->Run();
   }
 
@@ -55,19 +53,21 @@ class RendererOverridesHandlerTest : public ContentBrowserTest,
   }
 
   scoped_ptr<base::DictionaryValue> result_;
+  scoped_refptr<DevToolsAgentHost> agent_host_;
 
  private:
   virtual void SetUpOnMainThread() OVERRIDE {
-    DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-        DevToolsAgentHost::GetOrCreateFor(shell()->web_contents()).get(), this);
+    agent_host_ = DevToolsAgentHost::GetOrCreateFor(shell()->web_contents());
+    agent_host_->AttachClient(this);
   }
 
   virtual void TearDownOnMainThread() OVERRIDE {
-    DevToolsManager::GetInstance()->ClientHostClosing(this);
+    agent_host_->DetachClient();
+    agent_host_ = NULL;
   }
 
-  virtual void DispatchOnInspectorFrontend(
-      const std::string& message) OVERRIDE {
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE {
     scoped_ptr<base::DictionaryValue> root(
         static_cast<base::DictionaryValue*>(base::JSONReader::Read(message)));
     base::DictionaryValue* result;
@@ -76,11 +76,8 @@ class RendererOverridesHandlerTest : public ContentBrowserTest,
     base::MessageLoop::current()->QuitNow();
   }
 
-  virtual void InspectedContentsClosing() OVERRIDE {
-    EXPECT_TRUE(false);
-  }
-
-  virtual void ReplacedWithAnotherClient() OVERRIDE {
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host, bool replaced) OVERRIDE {
     EXPECT_TRUE(false);
   }
 };
diff --git a/content/browser/devtools/tethering_handler.cc b/content/browser/devtools/tethering_handler.cc
index 9b3b7fa..261338a 100644
--- a/content/browser/devtools/tethering_handler.cc
+++ b/content/browser/devtools/tethering_handler.cc
@@ -9,7 +9,6 @@
 #include "base/stl_util.h"
 #include "base/values.h"
 #include "content/browser/devtools/devtools_http_handler_impl.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_http_handler_delegate.h"
 #include "net/base/io_buffer.h"
 #include "net/base/ip_endpoint.h"
diff --git a/content/browser/service_worker/service_worker_internals_ui.cc b/content/browser/service_worker/service_worker_internals_ui.cc
index 1421fe4..a36cb66 100644
--- a/content/browser/service_worker/service_worker_internals_ui.cc
+++ b/content/browser/service_worker/service_worker_internals_ui.cc
@@ -11,6 +11,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/values.h"
+#include "content/browser/devtools/devtools_agent_host_impl.h"
 #include "content/browser/devtools/devtools_manager_impl.h"
 #include "content/browser/devtools/embedded_worker_devtools_manager.h"
 #include "content/browser/service_worker/service_worker_context_observer.h"
@@ -621,15 +622,14 @@ void ServiceWorkerInternalsUI::InspectWorker(const ListValue* args) {
   }
   base::Callback<void(ServiceWorkerStatusCode)> callback =
       base::Bind(OperationCompleteCallback, AsWeakPtr(), callback_id);
-  scoped_refptr<DevToolsAgentHost> agent_host(
+  scoped_refptr<DevToolsAgentHostImpl> agent_host(
       EmbeddedWorkerDevToolsManager::GetInstance()
           ->GetDevToolsAgentHostForWorker(process_id, devtools_agent_route_id));
   if (!agent_host) {
     callback.Run(SERVICE_WORKER_ERROR_NOT_FOUND);
     return;
   }
-  DevToolsManagerImpl::GetInstance()->Inspect(
-      web_ui()->GetWebContents()->GetBrowserContext(), agent_host.get());
+  agent_host->Inspect(web_ui()->GetWebContents()->GetBrowserContext());
   callback.Run(SERVICE_WORKER_OK);
 }
 
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index 2fc2c8e3..bce96fb 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -96,14 +96,13 @@
       'public/browser/desktop_media_id.h',
       'public/browser/desktop_notification_delegate.h',
       'public/browser/devtools_agent_host.h',
-      'public/browser/devtools_client_host.h',
+      'public/browser/devtools_agent_host_client.h',
       'public/browser/devtools_external_agent_proxy.h',
       'public/browser/devtools_external_agent_proxy_delegate.h',
       'public/browser/download_danger_type.h',
       'public/browser/devtools_frontend_host.h',
       'public/browser/devtools_http_handler.h',
       'public/browser/devtools_http_handler_delegate.h',
-      'public/browser/devtools_manager.h',
       'public/browser/devtools_manager_delegate.h',
       'public/browser/devtools_target.h',
       'public/browser/dom_operation_notification_details.h',
diff --git a/content/public/browser/devtools_agent_host.h b/content/public/browser/devtools_agent_host.h
index be02843..c424650 100644
--- a/content/public/browser/devtools_agent_host.h
+++ b/content/public/browser/devtools_agent_host.h
@@ -9,8 +9,10 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "content/common/content_export.h"
+#include "content/public/browser/devtools_agent_host_client.h"
 
 namespace content {
 
@@ -49,9 +51,18 @@ class CONTENT_EXPORT DevToolsAgentHost
   // Returns a list of all existing WebContents that can be debugged.
   static std::vector<WebContents*> GetInspectableWebContents();
 
+  // Client attaches to this agent host to start debugging it.
+  virtual void AttachClient(DevToolsAgentHostClient* client) = 0;
+
+  // Already attached client detaches from this agent host to stop debugging it.
+  virtual void DetachClient() = 0;
+
   // Returns true if there is a client attached.
   virtual bool IsAttached() = 0;
 
+  // Sends a message to the agent.
+  virtual void DispatchProtocolMessage(const std::string& message) = 0;
+
   // Starts inspecting element at position (|x|, |y|) in the specified page.
   virtual void InspectElement(int x, int y) = 0;
 
@@ -71,6 +82,15 @@ class CONTENT_EXPORT DevToolsAgentHost
   // Returns true if DevToolsAgentHost is for worker.
   virtual bool IsWorker() const = 0;
 
+  // Terminates all debugging sessions and detaches all clients.
+  static void DetachAllClients();
+
+  typedef base::Callback<void(DevToolsAgentHost*, bool attached)>
+      AgentStateCallback;
+
+  static void AddAgentStateCallback(const AgentStateCallback& callback);
+  static void RemoveAgentStateCallback(const AgentStateCallback& callback);
+
  protected:
   friend class base::RefCounted<DevToolsAgentHost>;
   virtual ~DevToolsAgentHost() {}
diff --git a/content/public/browser/devtools_agent_host_client.h b/content/public/browser/devtools_agent_host_client.h
new file mode 100644
index 0000000..90d7a73
--- /dev/null
+++ b/content/public/browser/devtools_agent_host_client.h
@@ -0,0 +1,34 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_BROWSER_DEVTOOLS_AGENT_HOST_CLIENT_H_
+#define CONTENT_PUBLIC_BROWSER_DEVTOOLS_AGENT_HOST_CLIENT_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class DevToolsAgentHost;
+
+// DevToolsAgentHostClient can attach to a DevToolsAgentHost and start
+// debugging it.
+class CONTENT_EXPORT DevToolsAgentHostClient {
+ public:
+  virtual ~DevToolsAgentHostClient() {}
+
+  // Dispatches given protocol message on the client.
+  virtual void DispatchProtocolMessage(DevToolsAgentHost* agent_host,
+                                       const std::string& message) = 0;
+
+  // This method is called when attached agent host is closed.
+  virtual void AgentHostClosed(DevToolsAgentHost* agent_host,
+                               bool replaced_with_another_client) = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_DEVTOOLS_AGENT_HOST_CLIENT_H_
diff --git a/content/public/browser/devtools_client_host.h b/content/public/browser/devtools_client_host.h
deleted file mode 100644
index 67b7003..0000000
--- a/content/public/browser/devtools_client_host.h
+++ /dev/null
@@ -1,45 +0,0 @@
-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_PUBLIC_BROWSER_DEVTOOLS_CLIENT_HOST_H_
-#define CONTENT_PUBLIC_BROWSER_DEVTOOLS_CLIENT_HOST_H_
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "content/common/content_export.h"
-
-namespace IPC {
-class Message;
-}
-
-namespace content {
-
-class RenderViewHost;
-class WebContents;
-
-class DevToolsFrontendHostDelegate;
-
-// Describes interface for managing devtools clients from browser process. There
-// are currently two types of clients: devtools windows and TCP socket
-// debuggers.
-class CONTENT_EXPORT DevToolsClientHost {
- public:
-  virtual ~DevToolsClientHost() {}
-
-  // Dispatches given message on the front-end.
-  virtual void DispatchOnInspectorFrontend(const std::string& message) = 0;
-
-  // This method is called when the contents inspected by this devtools client
-  // is closing.
-  virtual void InspectedContentsClosing() = 0;
-
-  // Called to notify client that it has been kicked out by some other client
-  // with greater priority.
-  virtual void ReplacedWithAnotherClient() = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_DEVTOOLS_CLIENT_HOST_H_
diff --git a/content/public/browser/devtools_manager.h b/content/public/browser/devtools_manager.h
deleted file mode 100644
index 32082ea..0000000
--- a/content/public/browser/devtools_manager.h
+++ /dev/null
@@ -1,65 +0,0 @@
-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_PUBLIC_BROWSER_DEVTOOLS_MANAGER_H_
-#define CONTENT_PUBLIC_BROWSER_DEVTOOLS_MANAGER_H_
-
-#include <string>
-
-#include "base/callback.h"
-#include "content/common/content_export.h"
-
-namespace IPC {
-class Message;
-}
-
-namespace content {
-
-class DevToolsAgentHost;
-class DevToolsClientHost;
-
-// DevToolsManager connects a devtools client to inspected agent and routes
-// devtools messages between the inspected instance represented by the agent
-// and devtools front-end represented by the client. If inspected agent
-// gets terminated DevToolsManager will notify corresponding client and
-// remove it from the map.
-class CONTENT_EXPORT DevToolsManager {
- public:
-  static DevToolsManager* GetInstance();
-
-  virtual ~DevToolsManager() {}
-
-  // Routes devtools message from |from| client to corresponding
-  // DevToolsAgentHost.
-  virtual bool DispatchOnInspectorBackend(DevToolsClientHost* from,
-                                          const std::string& message) = 0;
-
-  // Disconnects all client hostst.
-  virtual void CloseAllClientHosts() = 0;
-
-  // Returns agent that has |client_host| attached to it if there is one.
-  virtual DevToolsAgentHost* GetDevToolsAgentHostFor(
-      DevToolsClientHost* client_host) = 0;
-
-  // Registers new DevToolsClientHost for inspected |agent_host|. If there is
-  // another DevToolsClientHost registered for the |agent_host| at the moment
-  // it is disconnected.
-  virtual void RegisterDevToolsClientHostFor(
-      DevToolsAgentHost* agent_host,
-      DevToolsClientHost* client_host) = 0;
-
-  // This method will remove all references from the manager to the
-  // DevToolsClientHost and unregister all listeners related to the
-  // DevToolsClientHost. Called by closing client.
-  virtual void ClientHostClosing(DevToolsClientHost* client_host) = 0;
-
-  typedef base::Callback<void(DevToolsAgentHost*, bool attached)> Callback;
-
-  virtual void AddAgentStateCallback(const Callback& callback) = 0;
-  virtual void RemoveAgentStateCallback(const Callback& callback) = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_DEVTOOLS_MANAGER_H_
diff --git a/content/shell/browser/shell.cc b/content/shell/browser/shell.cc
index c63ff15..b10943d 100644
--- a/content/shell/browser/shell.cc
+++ b/content/shell/browser/shell.cc
@@ -12,7 +12,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
-#include "content/public/browser/devtools_manager.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/render_view_host.h"
@@ -114,7 +114,7 @@ Shell* Shell::CreateShell(WebContents* web_contents,
 
 void Shell::CloseAllWindows() {
   base::AutoReset<bool> auto_reset(&quit_message_loop_, false);
-  DevToolsManager::GetInstance()->CloseAllClientHosts();
+  DevToolsAgentHost::DetachAllClients();
   std::vector<Shell*> open_windows(windows_);
   for (size_t i = 0; i < open_windows.size(); ++i)
     open_windows[i]->Close();
diff --git a/content/shell/browser/shell_devtools_frontend.cc b/content/shell/browser/shell_devtools_frontend.cc
index a426020..b4abeef 100644
--- a/content/shell/browser/shell_devtools_frontend.cc
+++ b/content/shell/browser/shell_devtools_frontend.cc
@@ -11,7 +11,6 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/devtools_http_handler.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
@@ -116,8 +115,7 @@ void ShellDevToolsFrontend::RenderViewCreated(
     RenderViewHost* render_view_host) {
   if (!frontend_host_) {
     frontend_host_.reset(DevToolsFrontendHost::Create(render_view_host, this));
-    DevToolsManager::GetInstance()->RegisterDevToolsClientHostFor(
-        agent_host_.get(), this);
+    agent_host_->AttachClient(this);
   }
 }
 
@@ -127,7 +125,7 @@ void ShellDevToolsFrontend::DocumentOnLoadCompletedInMainFrame() {
 }
 
 void ShellDevToolsFrontend::WebContentsDestroyed() {
-  DevToolsManager::GetInstance()->ClientHostClosing(this);
+  agent_host_->DetachClient();
   delete this;
 }
 
@@ -159,8 +157,7 @@ void ShellDevToolsFrontend::HandleMessageFromDevToolsFrontend(
   }
   dict->GetInteger("id", &id);
 
-  DevToolsManager::GetInstance()->DispatchOnInspectorBackend(
-      this, browser_message);
+  agent_host_->DispatchProtocolMessage(browser_message);
 
   if (id) {
     std::string code = "InspectorFrontendAPI.embedderMessageAck(" +
@@ -172,18 +169,18 @@ void ShellDevToolsFrontend::HandleMessageFromDevToolsFrontend(
 
 void ShellDevToolsFrontend::HandleMessageFromDevToolsFrontendToBackend(
     const std::string& message) {
-  DevToolsManager::GetInstance()->DispatchOnInspectorBackend(
-      this, message);
+  agent_host_->DispatchProtocolMessage(message);
 }
 
-void ShellDevToolsFrontend::DispatchOnInspectorFrontend(
-    const std::string& message) {
+void ShellDevToolsFrontend::DispatchProtocolMessage(
+    DevToolsAgentHost* agent_host, const std::string& message) {
   std::string code = "InspectorFrontendAPI.dispatchMessage(" + message + ");";
   base::string16 javascript = base::UTF8ToUTF16(code);
   web_contents()->GetMainFrame()->ExecuteJavaScript(javascript);
 }
 
-void ShellDevToolsFrontend::InspectedContentsClosing() {
+void ShellDevToolsFrontend::AgentHostClosed(
+    DevToolsAgentHost* agent_host, bool replaced) {
   frontend_shell_->Close();
 }
 
diff --git a/content/shell/browser/shell_devtools_frontend.h b/content/shell/browser/shell_devtools_frontend.h
index 0c7f259..2d2eba6 100644
--- a/content/shell/browser/shell_devtools_frontend.h
+++ b/content/shell/browser/shell_devtools_frontend.h
@@ -10,7 +10,6 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_client_host.h"
 #include "content/public/browser/devtools_frontend_host.h"
 #include "content/public/browser/web_contents_observer.h"
 
@@ -25,7 +24,7 @@ class WebContents;
 
 class ShellDevToolsFrontend : public WebContentsObserver,
                               public DevToolsFrontendHost::Delegate,
-                              public DevToolsClientHost {
+                              public DevToolsAgentHostClient {
  public:
   static ShellDevToolsFrontend* Show(WebContents* inspected_contents);
   static ShellDevToolsFrontend* Show(WebContents* inspected_contents,
@@ -54,10 +53,11 @@ class ShellDevToolsFrontend : public WebContentsObserver,
   virtual void HandleMessageFromDevToolsFrontendToBackend(
       const std::string& message) OVERRIDE;
 
-  // content::DevToolsClientHost implementation.
-  virtual void DispatchOnInspectorFrontend(const std::string& message) OVERRIDE;
-  virtual void InspectedContentsClosing() OVERRIDE;
-  virtual void ReplacedWithAnotherClient() OVERRIDE {}
+  // content::DevToolsAgentHostClient implementation.
+  virtual void DispatchProtocolMessage(
+      DevToolsAgentHost* agent_host, const std::string& message) OVERRIDE;
+  virtual void AgentHostClosed(
+      DevToolsAgentHost* agent_host, bool replaced) OVERRIDE;
 
   Shell* frontend_shell_;
   scoped_refptr<DevToolsAgentHost> agent_host_;
diff --git a/content/shell/browser/webkit_test_controller.cc b/content/shell/browser/webkit_test_controller.cc
index 960f6a6..8fc8225 100644
--- a/content/shell/browser/webkit_test_controller.cc
+++ b/content/shell/browser/webkit_test_controller.cc
@@ -12,7 +12,7 @@
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
-#include "content/public/browser/devtools_manager.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/dom_storage_context.h"
 #include "content/public/browser/gpu_data_manager.h"
 #include "content/public/browser/navigation_controller.h"
@@ -653,7 +653,7 @@ void WebKitTestController::OnCaptureSessionHistory() {
 }
 
 void WebKitTestController::OnCloseRemainingWindows() {
-  DevToolsManager::GetInstance()->CloseAllClientHosts();
+  DevToolsAgentHost::DetachAllClients();
   std::vector<Shell*> open_windows(Shell::windows());
   for (size_t i = 0; i < open_windows.size(); ++i) {
     if (open_windows[i] != main_window_)
diff --git a/extensions/browser/process_manager.cc b/extensions/browser/process_manager.cc
index fc45e69..1a967ac 100644
--- a/extensions/browser/process_manager.cc
+++ b/extensions/browser/process_manager.cc
@@ -16,7 +16,6 @@
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/devtools_agent_host.h"
-#include "content/public/browser/devtools_manager.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
@@ -286,8 +285,7 @@ ProcessManager::ProcessManager(BrowserContext* context,
         base::TimeDelta::FromMilliseconds(suspending_time_msec);
   }
 
-  content::DevToolsManager::GetInstance()->AddAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::AddAgentStateCallback(devtools_callback_);
 
   OnKeepaliveImpulseCheck();
 }
@@ -295,8 +293,7 @@ ProcessManager::ProcessManager(BrowserContext* context,
 ProcessManager::~ProcessManager() {
   CloseBackgroundHosts();
   DCHECK(background_hosts_.empty());
-  content::DevToolsManager::GetInstance()->RemoveAgentStateCallback(
-      devtools_callback_);
+  content::DevToolsAgentHost::RemoveAgentStateCallback(devtools_callback_);
 }
 
 const ProcessManager::ViewSet ProcessManager::GetAllViews() const {