Revert "FBTF: Move the TabRestoreService::Observer into its own file."

chrome/browser/sessions/tab_restore_service.h

Index: chrome/browser/sessions/tab_restore_service.h
diff --git a/chrome/browser/sessions/tab_restore_service.h b/chrome/browser/sessions/tab_restore_service.h
index 2f9a237b00fd78ea3bf2272e86e8c6891f2f00b6..e12b9d1fc974d875461bebf3c4c42983278234e2 100644
--- a/chrome/browser/sessions/tab_restore_service.h
+++ b/chrome/browser/sessions/tab_restore_service.h
@@ -20,7 +20,6 @@ class Browser;
 class NavigationController;
 class Profile;
 struct SessionWindow;
-class TabRestoreServiceObserver;
 
 // TabRestoreService is responsible for maintaining the most recently closed
 // tabs and windows. When a tab is closed
@@ -35,6 +34,21 @@ class TabRestoreServiceObserver;
 // add an observer.
 class TabRestoreService : public BaseSessionService {
  public:
+  // Observer is notified when the set of entries managed by TabRestoreService
+  // changes in some way.
+  class Observer {
+   public:
+    // Sent when the set of entries changes in some way.
+    virtual void TabRestoreServiceChanged(TabRestoreService* service) = 0;
+
+    // Sent to all remaining Observers when TabRestoreService's
+    // destructor is run.
+    virtual void TabRestoreServiceDestroyed(TabRestoreService* service) = 0;
+
+   protected:
+    virtual ~Observer() {}
+  };
+
   // Interface used to allow the test to provide a custom time.
   class TimeFactory {
    public:
@@ -118,8 +132,8 @@ class TabRestoreService : public BaseSessionService {
 
   // Adds/removes an observer. TabRestoreService does not take ownership of
   // the observer.
-  void AddObserver(TabRestoreServiceObserver* observer);
-  void RemoveObserver(TabRestoreServiceObserver* observer);
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
 
   // Creates a Tab to represent |tab| and notifies observers the list of
   // entries has changed.
@@ -314,7 +328,7 @@ class TabRestoreService : public BaseSessionService {
   // Number of entries we've written.
   int entries_written_;
 
-  ObserverList<TabRestoreServiceObserver> observer_list_;
+  ObserverList<Observer> observer_list_;
 
   // Set of tabs that we've received a BrowserClosing method for but no
   // corresponding BrowserClosed. We cache the set of browsers closing to