Refactor code that defers extension background page loading

src/extensions depends on chrome::NOTIFICATION_PROFILE_CREATED to support deferred loading of extension background pages when the profile isn't ready yet. This is a layering violation.

* Remove Chrome concepts like "browser window ready" and "profile created" from ProcessManager. Introduce ProcessManagerDelegate with a general concept of deferring background page loading.
* Consolidate all the tricky Chrome-specific background page loading rules into ChromeProcessManagerDelegate. This keeps all the rules in one place. Annotate each block of special case code with the bug that inspired it.
* Extend unit test coverage for ProcessManager.

This will make it easier to eliminate chrome::NOTIFICATION_PROFILE_DESTROYED in ProcessManager in a later CL.

BUG=392658
TEST=unit_tests ProcessManagerTest, browser_tests ProcessManagerBrowserTest, manual

Review URL: https://codereview.chromium.org/381283002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283678 0039d316-1c4b-4281-b951-d872f2087c98

9 files changed, 231 insertions, 87 deletions

diff --git a/extensions/DEPS b/extensions/DEPS
index 0505b02..4077a55 100644
--- a/extensions/DEPS
+++ b/extensions/DEPS
@@ -1,4 +1,5 @@
 include_rules = [
+  # Do not add Chrome dependencies. Much work went into removing them.
   "+components/url_matcher",
   "+content/public/common",
   "+content/public/test",
@@ -13,7 +14,7 @@ include_rules = [
   # NOTE: Please do not add includes without talking to the app shell team;
   # see OWNERS for this directory.
   #
-  # TODO(jamescook): Remove these. http://crbug.com/162530
+  # TODO(jamescook): Remove this. http://crbug.com/392622
   "!chrome/browser/chrome_notification_types.h",
 ]
 
diff --git a/extensions/browser/extensions_browser_client.h b/extensions/browser/extensions_browser_client.h
index 293b2af..cb810b6 100644
--- a/extensions/browser/extensions_browser_client.h
+++ b/extensions/browser/extensions_browser_client.h
@@ -41,6 +41,7 @@ class ExtensionPrefsObserver;
 class ExtensionSystem;
 class ExtensionSystemProvider;
 class InfoMap;
+class ProcessManagerDelegate;
 class RuntimeAPIDelegate;
 
 // Interface to allow the extensions module to make browser-process-specific
@@ -133,12 +134,9 @@ class ExtensionsBrowserClient {
       content::BrowserContext* context,
       std::vector<ExtensionPrefsObserver*>* observers) const = 0;
 
-  // Returns true if loading background pages should be deferred.
-  virtual bool DeferLoadingBackgroundHosts(
-      content::BrowserContext* context) const = 0;
-
-  virtual bool IsBackgroundPageAllowed(
-      content::BrowserContext* context) const = 0;
+  // Returns the ProcessManagerDelegate shared across all BrowserContexts. May
+  // return NULL in tests or for simple embedders.
+  virtual ProcessManagerDelegate* GetProcessManagerDelegate() const = 0;
 
   // Creates a new ExtensionHostDelegate instance.
   virtual scoped_ptr<ExtensionHostDelegate> CreateExtensionHostDelegate() = 0;
diff --git a/extensions/browser/process_manager.cc b/extensions/browser/process_manager.cc
index e6beddb..12afd7c 100644
--- a/extensions/browser/process_manager.cc
+++ b/extensions/browser/process_manager.cc
@@ -33,6 +33,7 @@
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/extensions_browser_client.h"
+#include "extensions/browser/process_manager_delegate.h"
 #include "extensions/browser/process_manager_observer.h"
 #include "extensions/browser/view_type_utils.h"
 #include "extensions/common/constants.h"
@@ -245,8 +246,6 @@ ProcessManager::ProcessManager(BrowserContext* context,
                  content::NotificationService::AllSources());
   registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_CONNECTED,
                  content::NotificationService::AllSources());
-  registrar_.Add(this, chrome::NOTIFICATION_PROFILE_CREATED,
-                 content::Source<BrowserContext>(original_context));
   registrar_.Add(this, chrome::NOTIFICATION_PROFILE_DESTROYED,
                  content::Source<BrowserContext>(context));
   if (context->IsOffTheRecord()) {
@@ -307,11 +306,14 @@ bool ProcessManager::CreateBackgroundHost(const Extension* extension,
                                           const GURL& url) {
   // Hosted apps are taken care of from BackgroundContentsService. Ignore them
   // here.
-  if (extension->is_hosted_app() ||
-      !ExtensionsBrowserClient::Get()->
-          IsBackgroundPageAllowed(GetBrowserContext())) {
+  if (extension->is_hosted_app())
+    return false;
+
+  // Don't create hosts if the embedder doesn't allow it.
+  ProcessManagerDelegate* delegate =
+      ExtensionsBrowserClient::Get()->GetProcessManagerDelegate();
+  if (delegate && !delegate->IsBackgroundPageAllowed(GetBrowserContext()))
     return false;
-  }
 
   // Don't create multiple background hosts for an extension.
   if (GetBackgroundHostForExtension(extension->id()))
@@ -620,16 +622,6 @@ void ProcessManager::CancelSuspend(const Extension* extension) {
   }
 }
 
-void ProcessManager::OnBrowserWindowReady() {
-  // If the extension system isn't ready yet the background hosts will be
-  // created via NOTIFICATION_EXTENSIONS_READY below.
-  ExtensionSystem* system = ExtensionSystem::Get(GetBrowserContext());
-  if (!system->ready().is_signaled())
-    return;
-
-  CreateBackgroundHostsForProfileStartup();
-}
-
 content::BrowserContext* ProcessManager::GetBrowserContext() const {
   return site_instance_->GetBrowserContext();
 }
@@ -648,15 +640,10 @@ void ProcessManager::Observe(int type,
                              const content::NotificationSource& source,
                              const content::NotificationDetails& details) {
   switch (type) {
-    case chrome::NOTIFICATION_EXTENSIONS_READY:
-    case chrome::NOTIFICATION_PROFILE_CREATED: {
-       // Don't load background hosts now if the loading should be deferred.
-       // Instead they will be loaded when a browser window for this profile
-       // (or an incognito profile from this profile) is ready.
-       if (DeferLoadingBackgroundHosts())
-         break;
-
-      CreateBackgroundHostsForProfileStartup();
+    case chrome::NOTIFICATION_EXTENSIONS_READY: {
+      // TODO(jamescook): Convert this to use ExtensionSystem::ready() instead
+      // of a notification.
+      MaybeCreateStartupBackgroundHosts();
       break;
     }
 
@@ -784,24 +771,24 @@ void ProcessManager::OnDevToolsStateChanged(
   }
 }
 
-void ProcessManager::CreateBackgroundHostsForProfileStartup() {
-  if (startup_background_hosts_created_ ||
-      !ExtensionsBrowserClient::Get()->
-          IsBackgroundPageAllowed(GetBrowserContext())) {
+void ProcessManager::MaybeCreateStartupBackgroundHosts() {
+  if (startup_background_hosts_created_)
     return;
-  }
 
-  const ExtensionSet& enabled_extensions =
-      ExtensionRegistry::Get(GetBrowserContext())->enabled_extensions();
-  for (ExtensionSet::const_iterator extension = enabled_extensions.begin();
-       extension != enabled_extensions.end();
-       ++extension) {
-    CreateBackgroundHostForExtensionLoad(this, extension->get());
+  // The embedder might disallow background pages entirely.
+  ProcessManagerDelegate* delegate =
+      ExtensionsBrowserClient::Get()->GetProcessManagerDelegate();
+  if (delegate && !delegate->IsBackgroundPageAllowed(GetBrowserContext()))
+    return;
 
-    FOR_EACH_OBSERVER(ProcessManagerObserver,
-                      observer_list_,
-                      OnBackgroundHostStartup(*extension));
-  }
+  // The embedder might want to defer background page loading. For example,
+  // Chrome defers background page loading when it is launched to show the app
+  // list, then triggers a load later when a browser window opens.
+  if (delegate &&
+      delegate->DeferCreatingStartupBackgroundHosts(GetBrowserContext()))
+    return;
+
+  CreateStartupBackgroundHosts();
   startup_background_hosts_created_ = true;
 
   // Background pages should only be loaded once. To prevent any further loads
@@ -810,14 +797,6 @@ void ProcessManager::CreateBackgroundHostsForProfileStartup() {
       ExtensionsBrowserClient::Get()->GetOriginalContext(GetBrowserContext());
   if (registrar_.IsRegistered(
           this,
-          chrome::NOTIFICATION_PROFILE_CREATED,
-          content::Source<BrowserContext>(original_context))) {
-    registrar_.Remove(this,
-                      chrome::NOTIFICATION_PROFILE_CREATED,
-                      content::Source<BrowserContext>(original_context));
-  }
-  if (registrar_.IsRegistered(
-          this,
           chrome::NOTIFICATION_EXTENSIONS_READY,
           content::Source<BrowserContext>(original_context))) {
     registrar_.Remove(this,
@@ -826,6 +805,21 @@ void ProcessManager::CreateBackgroundHostsForProfileStartup() {
   }
 }
 
+void ProcessManager::CreateStartupBackgroundHosts() {
+  DCHECK(!startup_background_hosts_created_);
+  const ExtensionSet& enabled_extensions =
+      ExtensionRegistry::Get(GetBrowserContext())->enabled_extensions();
+  for (ExtensionSet::const_iterator extension = enabled_extensions.begin();
+       extension != enabled_extensions.end();
+       ++extension) {
+    CreateBackgroundHostForExtensionLoad(this, extension->get());
+
+    FOR_EACH_OBSERVER(ProcessManagerObserver,
+                      observer_list_,
+                      OnBackgroundHostStartup(*extension));
+  }
+}
+
 void ProcessManager::OnBackgroundHostCreated(ExtensionHost* host) {
   DCHECK_EQ(GetBrowserContext(), host->browser_context());
   background_hosts_.insert(host);
@@ -890,12 +884,6 @@ void ProcessManager::ClearBackgroundPageData(const std::string& extension_id) {
   }
 }
 
-bool ProcessManager::DeferLoadingBackgroundHosts() const {
-  // The extensions embedder may have special rules about background hosts.
-  return ExtensionsBrowserClient::Get()->DeferLoadingBackgroundHosts(
-      GetBrowserContext());
-}
-
 //
 // IncognitoProcessManager
 //
@@ -914,8 +902,6 @@ IncognitoProcessManager::IncognitoProcessManager(
   // in the NOTIFICATION_BROWSER_WINDOW_READY notification handler.
   registrar_.Remove(this, chrome::NOTIFICATION_EXTENSIONS_READY,
                     content::Source<BrowserContext>(original_context));
-  registrar_.Remove(this, chrome::NOTIFICATION_PROFILE_CREATED,
-                    content::Source<BrowserContext>(original_context));
 }
 
 bool IncognitoProcessManager::CreateBackgroundHost(const Extension* extension,
diff --git a/extensions/browser/process_manager.h b/extensions/browser/process_manager.h
index e580bbd..80736e4 100644
--- a/extensions/browser/process_manager.h
+++ b/extensions/browser/process_manager.h
@@ -33,6 +33,7 @@ namespace extensions {
 
 class Extension;
 class ExtensionHost;
+class ProcessManagerDelegate;
 class ProcessManagerObserver;
 
 // Manages dynamic state of running Chromium extensions. There is one instance
@@ -122,8 +123,9 @@ class ProcessManager : public content::NotificationObserver {
   // onSuspendCanceled() event to it.
   void CancelSuspend(const Extension* extension);
 
-  // Ensures background hosts are loaded for a new browser window.
-  void OnBrowserWindowReady();
+  // Creates background hosts if the embedder is ready and they are not already
+  // loaded.
+  void MaybeCreateStartupBackgroundHosts();
 
   // Gets the BrowserContext associated with site_instance_ and all other
   // related SiteInstances.
@@ -144,6 +146,10 @@ class ProcessManager : public content::NotificationObserver {
       content::BrowserContext* original_context,
       ProcessManager* original_manager);
 
+  bool startup_background_hosts_created_for_test() const {
+    return startup_background_hosts_created_;
+  }
+
  protected:
   // If |context| is incognito pass the master context as |original_context|.
   // Otherwise pass the same context for both.
@@ -158,10 +164,6 @@ class ProcessManager : public content::NotificationObserver {
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
-  // Load all background pages once the profile data is ready and the pages
-  // should be loaded.
-  void CreateBackgroundHostsForProfileStartup();
-
   content::NotificationRegistrar registrar_;
 
   // The set of ExtensionHosts running viewless background extensions.
@@ -182,6 +184,10 @@ class ProcessManager : public content::NotificationObserver {
   typedef std::map<content::RenderViewHost*,
       extensions::ViewType> ExtensionRenderViews;
 
+  // Load all background pages once the profile data is ready and the pages
+  // should be loaded.
+  void CreateStartupBackgroundHosts();
+
   // Called just after |host| is created so it can be registered in our lists.
   void OnBackgroundHostCreated(ExtensionHost* host);
 
@@ -216,9 +222,6 @@ class ProcessManager : public content::NotificationObserver {
   // Clears background page data for this extension.
   void ClearBackgroundPageData(const std::string& extension_id);
 
-  // Returns true if loading background pages should be deferred.
-  bool DeferLoadingBackgroundHosts() const;
-
   void OnDevToolsStateChanged(content::DevToolsAgentHost*, bool attached);
 
   // Contains all active extension-related RenderViewHost instances for all
diff --git a/extensions/browser/process_manager_delegate.h b/extensions/browser/process_manager_delegate.h
new file mode 100644
index 0000000..7cc48c0
--- /dev/null
+++ b/extensions/browser/process_manager_delegate.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 EXTENSIONS_BROWSER_PROCESS_MANAGER_DELEGATE_H_
+#define EXTENSIONS_BROWSER_PROCESS_MANAGER_DELEGATE_H_
+
+namespace content {
+class BrowserContext;
+};
+
+namespace extensions {
+
+// Customization of ProcessManager for the extension system embedder.
+class ProcessManagerDelegate {
+ public:
+  virtual ~ProcessManagerDelegate() {}
+
+  // Returns true if the embedder allows background pages for the given
+  // |context|.
+  virtual bool IsBackgroundPageAllowed(
+      content::BrowserContext* context) const = 0;
+
+  // Returns true if the embedder wishes to defer starting up the renderers for
+  // extension background pages. If the embedder returns true it must call
+  // ProcessManager::MaybeCreateStartupBackgroundHosts() when it is ready. See
+  // ChromeProcessManagerDelegate for examples of how this is useful.
+  virtual bool DeferCreatingStartupBackgroundHosts(
+      content::BrowserContext* context) const = 0;
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_PROCESS_MANAGER_DELEGATE_H_
diff --git a/extensions/browser/process_manager_unittest.cc b/extensions/browser/process_manager_unittest.cc
index b72b112..0d1f86b 100644
--- a/extensions/browser/process_manager_unittest.cc
+++ b/extensions/browser/process_manager_unittest.cc
@@ -5,10 +5,12 @@
 #include "extensions/browser/process_manager.h"
 
 #include "chrome/browser/chrome_notification_types.h"
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/test/test_browser_context.h"
+#include "extensions/browser/process_manager_delegate.h"
 #include "extensions/browser/test_extensions_browser_client.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -33,12 +35,35 @@ class TestBrowserContextIncognito : public TestBrowserContext {
   DISALLOW_COPY_AND_ASSIGN(TestBrowserContextIncognito);
 };
 
+// A trivial ProcessManagerDelegate.
+class TestProcessManagerDelegate : public ProcessManagerDelegate {
+ public:
+  TestProcessManagerDelegate()
+      : is_background_page_allowed_(true),
+        defer_creating_startup_background_hosts_(false) {}
+  virtual ~TestProcessManagerDelegate() {}
+
+  // ProcessManagerDelegate implementation.
+  virtual bool IsBackgroundPageAllowed(BrowserContext* context) const OVERRIDE {
+    return is_background_page_allowed_;
+  }
+  virtual bool DeferCreatingStartupBackgroundHosts(
+      BrowserContext* context) const OVERRIDE {
+    return defer_creating_startup_background_hosts_;
+  }
+
+  bool is_background_page_allowed_;
+  bool defer_creating_startup_background_hosts_;
+};
+
 }  // namespace
 
 class ProcessManagerTest : public testing::Test {
  public:
   ProcessManagerTest() : extensions_browser_client_(&original_context_) {
     extensions_browser_client_.SetIncognitoContext(&incognito_context_);
+    extensions_browser_client_.set_process_manager_delegate(
+        &process_manager_delegate_);
     ExtensionsBrowserClient::Set(&extensions_browser_client_);
   }
 
@@ -49,6 +74,23 @@ class ProcessManagerTest : public testing::Test {
   BrowserContext* original_context() { return &original_context_; }
   BrowserContext* incognito_context() { return &incognito_context_; }
 
+  // testing::Test implementation.
+  virtual void SetUp() OVERRIDE {
+    // Needed for ExtensionRegistry.
+    BrowserContextDependencyManager::GetInstance()
+        ->CreateBrowserContextServicesForTest(&original_context_);
+    BrowserContextDependencyManager::GetInstance()
+        ->CreateBrowserContextServicesForTest(&incognito_context_);
+  }
+
+  virtual void TearDown() OVERRIDE {
+    // Needed to clean up ExtensionRegistry.
+    BrowserContextDependencyManager::GetInstance()
+        ->DestroyBrowserContextServices(&incognito_context_);
+    BrowserContextDependencyManager::GetInstance()
+        ->DestroyBrowserContextServices(&original_context_);
+  }
+
   // Returns true if the notification |type| is registered for |manager| with
   // source |context|. Pass NULL for |context| for all sources.
   static bool IsRegistered(ProcessManager* manager,
@@ -58,9 +100,10 @@ class ProcessManagerTest : public testing::Test {
         manager, type, content::Source<BrowserContext>(context));
   }
 
- private:
+ protected:
   TestBrowserContext original_context_;
   TestBrowserContextIncognito incognito_context_;
+  TestProcessManagerDelegate process_manager_delegate_;
   TestExtensionsBrowserClient extensions_browser_client_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessManagerTest);
@@ -125,6 +168,83 @@ TEST_F(ProcessManagerTest, ExtensionNotificationRegistration) {
                            incognito_context()));
 }
 
+// Test that startup background hosts are created when the extension system
+// becomes ready.
+//
+// NOTE: This test and those that follow do not try to create ExtensionsHosts
+// because ExtensionHost is tightly coupled to WebContents and can't be
+// constructed in unit tests.
+TEST_F(ProcessManagerTest, CreateBackgroundHostsOnExtensionsReady) {
+  scoped_ptr<ProcessManager> manager(
+      ProcessManager::Create(original_context()));
+  ASSERT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // Simulate the extension system becoming ready.
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_EXTENSIONS_READY,
+      content::Source<BrowserContext>(original_context()),
+      content::NotificationService::NoDetails());
+  EXPECT_TRUE(manager->startup_background_hosts_created_for_test());
+}
+
+// Test that startup background hosts can be created explicitly before the
+// extension system is ready (this is the normal pattern in Chrome).
+TEST_F(ProcessManagerTest, CreateBackgroundHostsExplicitly) {
+  scoped_ptr<ProcessManager> manager(
+      ProcessManager::Create(original_context()));
+  ASSERT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // Embedder explicitly asks for hosts to be created. Chrome does this on
+  // normal startup.
+  manager->MaybeCreateStartupBackgroundHosts();
+  EXPECT_TRUE(manager->startup_background_hosts_created_for_test());
+}
+
+// Test that the embedder can defer background host creation. Chrome does this
+// when the profile is created asynchronously, which may take a while.
+TEST_F(ProcessManagerTest, CreateBackgroundHostsDeferred) {
+  scoped_ptr<ProcessManager> manager(
+      ProcessManager::Create(original_context()));
+  ASSERT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // Don't create background hosts if the delegate says to defer them.
+  process_manager_delegate_.defer_creating_startup_background_hosts_ = true;
+  manager->MaybeCreateStartupBackgroundHosts();
+  EXPECT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // The extension system becoming ready still doesn't create the hosts.
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_EXTENSIONS_READY,
+      content::Source<BrowserContext>(original_context()),
+      content::NotificationService::NoDetails());
+  EXPECT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // Once the embedder is ready the background hosts can be created.
+  process_manager_delegate_.defer_creating_startup_background_hosts_ = false;
+  manager->MaybeCreateStartupBackgroundHosts();
+  EXPECT_TRUE(manager->startup_background_hosts_created_for_test());
+}
+
+// Test that the embedder can disallow background host creation.
+// Chrome OS does this in guest mode.
+TEST_F(ProcessManagerTest, IsBackgroundHostAllowed) {
+  scoped_ptr<ProcessManager> manager(
+      ProcessManager::Create(original_context()));
+  ASSERT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // Don't create background hosts if the delegate disallows them.
+  process_manager_delegate_.is_background_page_allowed_ = false;
+  manager->MaybeCreateStartupBackgroundHosts();
+  EXPECT_FALSE(manager->startup_background_hosts_created_for_test());
+
+  // The extension system becoming ready still doesn't create the hosts.
+  content::NotificationService::current()->Notify(
+      chrome::NOTIFICATION_EXTENSIONS_READY,
+      content::Source<BrowserContext>(original_context()),
+      content::NotificationService::NoDetails());
+  EXPECT_FALSE(manager->startup_background_hosts_created_for_test());
+}
+
 // Test that extensions get grouped in the right SiteInstance (and therefore
 // process) based on their URLs.
 TEST_F(ProcessManagerTest, ProcessGrouping) {
diff --git a/extensions/browser/test_extensions_browser_client.cc b/extensions/browser/test_extensions_browser_client.cc
index dcd467f..a01b128 100644
--- a/extensions/browser/test_extensions_browser_client.cc
+++ b/extensions/browser/test_extensions_browser_client.cc
@@ -15,7 +15,9 @@ namespace extensions {
 
 TestExtensionsBrowserClient::TestExtensionsBrowserClient(
     BrowserContext* main_context)
-    : main_context_(main_context), incognito_context_(NULL) {
+    : main_context_(main_context),
+      incognito_context_(NULL),
+      process_manager_delegate_(NULL) {
   DCHECK(main_context_);
   DCHECK(!main_context_->IsOffTheRecord());
 }
@@ -116,14 +118,9 @@ void TestExtensionsBrowserClient::GetEarlyExtensionPrefsObservers(
     content::BrowserContext* context,
     std::vector<ExtensionPrefsObserver*>* observers) const {}
 
-bool TestExtensionsBrowserClient::DeferLoadingBackgroundHosts(
-    BrowserContext* context) const {
-  return false;
-}
-
-bool TestExtensionsBrowserClient::IsBackgroundPageAllowed(
-    BrowserContext* context) const {
-  return true;
+ProcessManagerDelegate* TestExtensionsBrowserClient::GetProcessManagerDelegate()
+    const {
+  return process_manager_delegate_;
 }
 
 scoped_ptr<ExtensionHostDelegate>
diff --git a/extensions/browser/test_extensions_browser_client.h b/extensions/browser/test_extensions_browser_client.h
index b793259..1cfffee 100644
--- a/extensions/browser/test_extensions_browser_client.h
+++ b/extensions/browser/test_extensions_browser_client.h
@@ -15,10 +15,14 @@ namespace extensions {
 // this class should call ExtensionsBrowserClient::Set() with its instance.
 class TestExtensionsBrowserClient : public ExtensionsBrowserClient {
  public:
-  // |context| is required and must not be an incognito context.
+  // |main_context| is required and must not be an incognito context.
   explicit TestExtensionsBrowserClient(content::BrowserContext* main_context);
   virtual ~TestExtensionsBrowserClient();
 
+  void set_process_manager_delegate(ProcessManagerDelegate* delegate) {
+    process_manager_delegate_ = delegate;
+  }
+
   // Associates an incognito context with |main_context_|.
   void SetIncognitoContext(content::BrowserContext* incognito_context);
 
@@ -59,10 +63,7 @@ class TestExtensionsBrowserClient : public ExtensionsBrowserClient {
   virtual void GetEarlyExtensionPrefsObservers(
       content::BrowserContext* context,
       std::vector<ExtensionPrefsObserver*>* observers) const OVERRIDE;
-  virtual bool DeferLoadingBackgroundHosts(
-      content::BrowserContext* context) const OVERRIDE;
-  virtual bool IsBackgroundPageAllowed(content::BrowserContext* context) const
-      OVERRIDE;
+  virtual ProcessManagerDelegate* GetProcessManagerDelegate() const OVERRIDE;
   virtual scoped_ptr<ExtensionHostDelegate> CreateExtensionHostDelegate()
       OVERRIDE;
   virtual bool DidVersionUpdate(content::BrowserContext* context) OVERRIDE;
@@ -82,6 +83,9 @@ class TestExtensionsBrowserClient : public ExtensionsBrowserClient {
   content::BrowserContext* main_context_;       // Not owned.
   content::BrowserContext* incognito_context_;  // Not owned, defaults to NULL.
 
+  // Not owned, defaults to NULL.
+  ProcessManagerDelegate* process_manager_delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(TestExtensionsBrowserClient);
 };
 
diff --git a/extensions/extensions.gyp b/extensions/extensions.gyp
index 4349183..3501961 100644
--- a/extensions/extensions.gyp
+++ b/extensions/extensions.gyp
@@ -435,6 +435,7 @@
         'browser/pref_names.h',
         'browser/process_manager.cc',
         'browser/process_manager.h',
+        'browser/process_manager_delegate.h',
         'browser/process_manager_observer.h',
         'browser/process_map.cc',
         'browser/process_map.h',