Use FrameTreeNode ID as frameId in extension APIs

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index 795bec5a678da5d77c5485d6e4a16b73063ecbd9..832894c785c8deae4f4e0113e4cc1c9ca1a6ae76 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -211,6 +211,10 @@ class WebContents : public PageNavigator,
   // Returns the focused frame for the currently active view.
   virtual RenderFrameHost* GetFocusedFrame() = 0;
 
+  // Returns the current RenderFrameHost for a given FrameTreeNode ID if it is
+  // part of this tab.
+  virtual RenderFrameHost* FindByFrameTreeNodeID(int frame_tree_node_id) = 0;

[Charlie Reis, 2015/11/03 00:23:49]

nit: FindFrameByFrameTreeNodeID

(Otherwise FindByX seems to implicitly mean FindWebContentsByX.)

[robwu, 2015/11/03 10:03:02]

Done.

+
   // 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