Move dispatching and sending of the last extension specific messages out of TabContents and Rende...

content/browser/tab_contents/tab_contents_observer.h

 // Copyright (c) 2011 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_BROWSER_TAB_CONTENTS_TAB_CONTENTS_OBSERVER_H_
 #define CONTENT_BROWSER_TAB_CONTENTS_TAB_CONTENTS_OBSERVER_H_
 
 #include "content/browser/tab_contents/navigation_controller.h"
 #include "ipc/ipc_channel.h"
 
 struct ViewHostMsg_FrameNavigate_Params;
 
 // An observer API implemented by classes which are interested in various page
 // load events from TabContents.  They also get a chance to filter IPC messages.
-class TabContentsObserver : public IPC::Channel::Listener {
+class TabContentsObserver : public IPC::Channel::Listener,
+                            public IPC::Message::Sender {
  public:
+  // Use this as a member variable in a class that uses the emptry constructor
+  // version of this interface.
+  class Registrar {
+   public:
+    explicit Registrar(TabContentsObserver* observer);
+    ~Registrar();
+
+    // Call this to start observing a tab.  Passing in NULL resets it.
+    // This can only be used to watch one tab at a time.  If you call this and
+    // you're already observing another tab, the old tab won't be observed
+    // afterwards.
+    void Observe(TabContents* tab);
+
+   private:
+    TabContentsObserver* observer_;
+    TabContents* tab_;
+
+    DISALLOW_COPY_AND_ASSIGN(Registrar);
+  };
+
   virtual void NavigateToPendingEntry();
 
   virtual void DidNavigateMainFramePostCommit(
       const NavigationController::LoadCommittedDetails& details,
       const ViewHostMsg_FrameNavigate_Params& params);
   virtual void DidNavigateAnyFramePostCommit(
       const NavigationController::LoadCommittedDetails& details,
       const ViewHostMsg_FrameNavigate_Params& params);
   virtual void OnProvisionalChangeToMainFrameUrl(const GURL& url);
 
@@ skipping 11 matching lines @@
   virtual void LoadingStateChanged(TabContents* contents) { }
   // Called to inform the delegate that the tab content's navigation state
   // changed. The |changed_flags| indicates the parts of the navigation state
   // that have been updated, and is any combination of the
   // |TabContents::InvalidateTypes| bits.
   virtual void NavigationStateChanged(const TabContents* source,
                                       unsigned changed_flags) { }
 #endif
 
  protected:
+  // Use this constructor when the object is tied to a single TabContents for
+  // its entire lifetime.
   explicit TabContentsObserver(TabContents* tab_contents);
+
+  // Use this constructor when the object wants to observe a TabContents for
+  // part of its lifetime.  It can use a TabContentsRegistrar member variable
+  // to start and stop observing.
+  TabContentsObserver();
+
   virtual ~TabContentsObserver();
 
   // Invoked when the TabContents is being destroyed. Gives subclasses a chance
   // to cleanup. At the time this is invoked |tab_contents()| returns NULL.
   // It is safe to delete 'this' from here.
   virtual void OnTabContentsDestroyed(TabContents* tab);
 
   // IPC::Channel::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message);
 
@@ skipping 12 matching lines @@
 
   TabContents* tab_contents_;
 
   // The routing ID of the associated TabContents.
   int routing_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TabContentsObserver);
 };
 
 #endif  // CONTENT_BROWSER_TAB_CONTENTS_TAB_CONTENTS_OBSERVER_H_