Introduce RenderFrameObserver.

content/renderer/render_frame_impl.h

Index: content/renderer/render_frame_impl.h
===================================================================
--- content/renderer/render_frame_impl.h	(revision 238191)
+++ content/renderer/render_frame_impl.h	(working copy)
@@ -10,6 +10,7 @@
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
+#include "base/observer_list.h"
 #include "base/process/process_handle.h"
 #include "base/strings/string16.h"
 #include "content/public/renderer/render_frame.h"
@@ -34,6 +35,7 @@
 
 class PepperPluginInstanceImpl;
 class RendererPpapiHost;
+class RenderFrameObserver;
 class RenderViewImpl;
 class RenderWidget;
 class RenderWidgetFullscreenPepper;
@@ -57,6 +59,8 @@
   // to using RenderFrame instead of RenderView.
   RenderViewImpl* render_view() { return render_view_; }
 
+  int routing_id() const { return routing_id_; }

[nasko, 2013/12/03 00:07:33]

nit: Why not keep the GetRoutingID() naming, which is present in RenderView? I
expect this will have to be in the public RenderFrame interface at some point.

[jam, 2013/12/03 00:14:31]

just because in general we have unix_hacker accessors for simple getters
sure, in that point we can then move it? I tend to prefer to not adding methods
until we know they're needed. Who knows, maybe this won't be needed on RF and in
which case the unix_hacker getter is enough.

+
   // Returns the RenderWidget associated with this frame.
   RenderWidget* GetRenderWidget();
 
@@ -301,8 +305,12 @@
   RenderFrameImpl(RenderViewImpl* render_view, int32 routing_id);
 
  private:
-  int GetRoutingID() const;
+  friend class RenderFrameObserver;
 
+  // Functions to add and remove observers for this object.
+  void AddObserver(RenderFrameObserver* observer);
+  void RemoveObserver(RenderFrameObserver* observer);
+
   RenderViewImpl* render_view_;
   int routing_id_;
   bool is_swapped_out_;
@@ -326,6 +334,9 @@
   PepperPluginInstanceImpl* pepper_last_mouse_event_target_;
 #endif
 
+  // All the registered observers.
+  ObserverList<RenderFrameObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };