Add onChanged callback for chrome.sessions API.

Currently there is no method to receive the changes of recently closed pages
in chrome.sessions APIs. This callback can give extensions a chance to know
there is a change and update by calling GetRecentlyClosed again.

R=kalman@chromium.org
BUG=353007

Review URL: https://codereview.chromium.org/201393002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260464 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 116 insertions, 0 deletions

diff --git a/chrome/browser/extensions/api/sessions/sessions_api.cc b/chrome/browser/extensions/api/sessions/sessions_api.cc
index eca014e..0774d82 100644
--- a/chrome/browser/extensions/api/sessions/sessions_api.cc
+++ b/chrome/browser/extensions/api/sessions/sessions_api.cc
@@ -35,6 +35,7 @@
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/extension_function_dispatcher.h"
 #include "extensions/browser/extension_function_registry.h"
+#include "extensions/browser/extension_system.h"
 #include "extensions/common/error_utils.h"
 #include "net/base/net_util.h"
 #include "ui/base/layout.h"
@@ -593,4 +594,59 @@ bool SessionsRestoreFunction::RunImpl() {
       : RestoreLocalSession(*session_id, browser);
 }
 
+SessionsEventRouter::SessionsEventRouter(Profile* profile)
+    : profile_(profile),
+      tab_restore_service_(TabRestoreServiceFactory::GetForProfile(profile)) {
+  // TabRestoreServiceFactory::GetForProfile() can return NULL (i.e., when in
+  // incognito mode)
+  if (tab_restore_service_) {
+    tab_restore_service_->LoadTabsFromLastSession();
+    tab_restore_service_->AddObserver(this);
+  }
+}
+
+SessionsEventRouter::~SessionsEventRouter() {
+  if (tab_restore_service_)
+    tab_restore_service_->RemoveObserver(this);
+}
+
+void SessionsEventRouter::TabRestoreServiceChanged(
+    TabRestoreService* service) {
+  scoped_ptr<base::ListValue> args(new base::ListValue());
+  EventRouter::Get(profile_)->BroadcastEvent(make_scoped_ptr(
+      new Event(api::sessions::OnChanged::kEventName, args.Pass())));
+}
+
+void SessionsEventRouter::TabRestoreServiceDestroyed(
+    TabRestoreService* service) {
+  tab_restore_service_ = NULL;
+}
+
+SessionsAPI::SessionsAPI(content::BrowserContext* context)
+    : browser_context_(context) {
+  EventRouter::Get(browser_context_)->RegisterObserver(this,
+      api::sessions::OnChanged::kEventName);
+}
+
+SessionsAPI::~SessionsAPI() {
+}
+
+void SessionsAPI::Shutdown() {
+  EventRouter::Get(browser_context_)->UnregisterObserver(this);
+}
+
+static base::LazyInstance<BrowserContextKeyedAPIFactory<SessionsAPI> >
+    g_factory = LAZY_INSTANCE_INITIALIZER;
+
+BrowserContextKeyedAPIFactory<SessionsAPI>*
+SessionsAPI::GetFactoryInstance() {
+  return g_factory.Pointer();
+}
+
+void SessionsAPI::OnListenerAdded(const EventListenerInfo& details) {
+  sessions_event_router_.reset(
+      new SessionsEventRouter(Profile::FromBrowserContext(browser_context_)));
+  EventRouter::Get(browser_context_)->UnregisterObserver(this);
+}
+
 }  // namespace extensions
diff --git a/chrome/browser/extensions/api/sessions/sessions_api.h b/chrome/browser/extensions/api/sessions/sessions_api.h
index e044019..49b00bb 100644
--- a/chrome/browser/extensions/api/sessions/sessions_api.h
+++ b/chrome/browser/extensions/api/sessions/sessions_api.h
@@ -13,6 +13,8 @@
 #include "chrome/common/extensions/api/sessions.h"
 #include "chrome/common/extensions/api/tabs.h"
 #include "chrome/common/extensions/api/windows.h"
+#include "extensions/browser/browser_context_keyed_api_factory.h"
+#include "extensions/browser/event_router.h"
 
 class Profile;
 
@@ -79,6 +81,62 @@ class SessionsRestoreFunction : public ChromeSyncExtensionFunction {
                              Browser* browser);
 };
 
+class SessionsEventRouter : public TabRestoreServiceObserver {
+ public:
+  explicit SessionsEventRouter(Profile* profile);
+  virtual ~SessionsEventRouter();
+
+  // Observer callback for TabRestoreServiceObserver. Sends data on
+  // recently closed tabs to the javascript side of this page to
+  // display to the user.
+  virtual void TabRestoreServiceChanged(TabRestoreService* service) OVERRIDE;
+
+  // Observer callback to notice when our associated TabRestoreService
+  // is destroyed.
+  virtual void TabRestoreServiceDestroyed(TabRestoreService* service) OVERRIDE;
+
+ private:
+  Profile* profile_;
+
+  // TabRestoreService that we are observing.
+  TabRestoreService* tab_restore_service_;
+
+  DISALLOW_COPY_AND_ASSIGN(SessionsEventRouter);
+};
+
+class SessionsAPI : public BrowserContextKeyedAPI,
+                    public extensions::EventRouter::Observer {
+ public:
+  explicit SessionsAPI(content::BrowserContext* context);
+  virtual ~SessionsAPI();
+
+  // BrowserContextKeyedService implementation.
+  virtual void Shutdown() OVERRIDE;
+
+  // BrowserContextKeyedAPI implementation.
+  static BrowserContextKeyedAPIFactory<SessionsAPI>* GetFactoryInstance();
+
+  // EventRouter::Observer implementation.
+  virtual void OnListenerAdded(const extensions::EventListenerInfo& details)
+      OVERRIDE;
+
+ private:
+  friend class BrowserContextKeyedAPIFactory<SessionsAPI>;
+
+  content::BrowserContext* browser_context_;
+
+  // BrowserContextKeyedAPI implementation.
+  static const char* service_name() {
+    return "SessionsAPI";
+  }
+  static const bool kServiceIsNULLWhileTesting = true;
+
+  // Created lazily upon OnListenerAdded.
+  scoped_ptr<SessionsEventRouter> sessions_event_router_;
+
+  DISALLOW_COPY_AND_ASSIGN(SessionsAPI);
+};
+
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SESSIONS_SESSIONS_API_H__
diff --git a/chrome/browser/extensions/browser_context_keyed_service_factories.cc b/chrome/browser/extensions/browser_context_keyed_service_factories.cc
index 7a4a27d..a3318f1 100644
--- a/chrome/browser/extensions/browser_context_keyed_service_factories.cc
+++ b/chrome/browser/extensions/browser_context_keyed_service_factories.cc
@@ -36,6 +36,7 @@
 #include "chrome/browser/extensions/api/push_messaging/push_messaging_api.h"
 #include "chrome/browser/extensions/api/runtime/runtime_api.h"
 #include "chrome/browser/extensions/api/serial/serial_connection.h"
+#include "chrome/browser/extensions/api/sessions/sessions_api.h"
 #include "chrome/browser/extensions/api/settings_overrides/settings_overrides_api.h"
 #include "chrome/browser/extensions/api/signed_in_devices/signed_in_devices_manager.h"
 #include "chrome/browser/extensions/api/streams_private/streams_private_api.h"
@@ -132,6 +133,7 @@ void EnsureBrowserContextKeyedServiceFactoriesBuilt() {
   extensions::ProcessesAPI::GetFactoryInstance();
   extensions::PushMessagingAPI::GetFactoryInstance();
   extensions::RuntimeAPI::GetFactoryInstance();
+  extensions::SessionsAPI::GetFactoryInstance();
   extensions::SettingsOverridesAPI::GetFactoryInstance();
   extensions::SignedInDevicesManager::GetFactoryInstance();
 #if defined(ENABLE_SPELLCHECK)