Use FrameTreeNode ID as frameId in extension APIs

content/browser/web_contents/web_contents_impl.cc

 // 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.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 753 matching lines @@
   return frame_tree_.root()->current_frame_host();
 }
 
 RenderFrameHostImpl* WebContentsImpl::GetFocusedFrame() {
   FrameTreeNode* focused_node = frame_tree_.GetFocusedFrame();
   if (!focused_node)
     return nullptr;
   return focused_node->current_frame_host();
 }
 
+RenderFrameHostImpl* WebContentsImpl::FindFrameByFrameTreeNodeId(
+    int frame_tree_node_id) {
+  FrameTreeNode* frame = frame_tree_.FindByID(frame_tree_node_id);
+  return frame ? frame->current_frame_host() : nullptr;
+}
+
 void WebContentsImpl::ForEachFrame(
     const base::Callback<void(RenderFrameHost*)>& on_frame) {
   frame_tree_.ForEach(base::Bind(&ForEachFrameInternal, on_frame));
 }
 
 void WebContentsImpl::SendToAllFrames(IPC::Message* message) {
   ForEachFrame(base::Bind(&SendToAllFramesInternal, message));
   delete message;
 }
 
@@ skipping 3937 matching lines @@
     const WebContentsObserver::MediaPlayerId& id) {
   FOR_EACH_OBSERVER(WebContentsObserver, observers_, MediaStartedPlaying(id));
 }
 
 void WebContentsImpl::MediaStoppedPlaying(
     const WebContentsObserver::MediaPlayerId& id) {
   FOR_EACH_OBSERVER(WebContentsObserver, observers_, MediaStoppedPlaying(id));
 }
 
 }  // namespace content