Add onChanged callback for chrome.sessions API.

chrome/browser/extensions/api/sessions/sessions_api.h

Index: chrome/browser/extensions/api/sessions/sessions_api.h
diff --git a/chrome/browser/extensions/api/sessions/sessions_api.h b/chrome/browser/extensions/api/sessions/sessions_api.h
index e04401937f3d2c90cb4835d05e83cabe8354a367..49b00bb55c4bdfd4cfe42e5884b803ec0f6a94ee 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__