Use FrameTreeNode ID as frameId in extension APIs

content/public/browser/render_frame_host.h

 // Copyright 2013 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_RENDER_FRAME_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_FRAME_HOST_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 46 matching lines @@
   virtual SiteInstance* GetSiteInstance() = 0;
 
   // Returns the process for this frame.
   virtual RenderProcessHost* GetProcess() = 0;
 
   // Returns the current RenderFrameHost of the parent frame, or nullptr if
   // there is no parent. The result may be in a different process than the
   // current RenderFrameHost.
   virtual RenderFrameHost* GetParent() = 0;
 
+  // Returns the FrameTreeNode ID for this frame.
+  virtual int GetFrameTreeNodeID() = 0;
+
   // Returns the assigned name of the frame, the name of the iframe tag
   // declaring it. For example, <iframe name="framename">[...]</iframe>. It is
   // quite possible for a frame to have no name, in which case GetFrameName will
   // return an empty string.
   virtual const std::string& GetFrameName() = 0;
 
   // Returns true if the frame is out of process.
   virtual bool IsCrossProcessSubframe() = 0;
 
   // Returns the last committed URL of the frame.
@@ skipping 73 matching lines @@
 
  private:
   // This interface should only be implemented inside content.
   friend class RenderFrameHostImpl;
   RenderFrameHost() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_FRAME_HOST_H_