Improve comments on WebContentsObserver RenderFrame* methods and rename.

content/public/browser/web_contents.h

 // Copyright (c) 2012 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_PUBLIC_BROWSER_WEB_CONTENTS_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_
 
 #include <set>
 
 #include "base/basictypes.h"
@@ skipping 174 matching lines @@
   // these may change over time.
   virtual RenderProcessHost* GetRenderProcessHost() const = 0;
 
   // Returns the main frame for the currently active view.
   virtual RenderFrameHost* GetMainFrame() = 0;
 
   // Returns the focused frame for the currently active view.
   virtual RenderFrameHost* GetFocusedFrame() = 0;
 
   // Calls |on_frame| for each frame in the currently active view.
+  // Note: The RenderFrameHost parameter is not guaranteed to have a live
+  // RenderFrame counterpart in the renderer process. Callbacks should check
+  // IsRenderFrameLive, as sending IPC messages to it in this case will fail
+  // silently.
   virtual void ForEachFrame(
       const base::Callback<void(RenderFrameHost*)>& on_frame) = 0;
 
   // Sends the given IPC to all frames in the currently active view. This is a
   // convenience method instead of calling ForEach.
   virtual void SendToAllFrames(IPC::Message* message) = 0;
 
   // Gets the current RenderViewHost for this tab.
   virtual RenderViewHost* GetRenderViewHost() const = 0;
 
@@ skipping 409 matching lines @@
 
  private:
   // This interface should only be implemented inside content.
   friend class WebContentsImpl;
   WebContents() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_H_