Use FrameTreeNode ID as frameId in extension APIs

content/browser/frame_host/render_frame_host_impl.cc

 // 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.
 
 #include "content/browser/frame_host/render_frame_host_impl.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
@@ skipping 255 matching lines @@
   return process_;
 }
 
 RenderFrameHost* RenderFrameHostImpl::GetParent() {
   FrameTreeNode* parent_node = frame_tree_node_->parent();
   if (!parent_node)
     return NULL;
   return parent_node->current_frame_host();
 }
 
+int RenderFrameHostImpl::GetFrameTreeNodeID() {
+  return frame_tree_node_->frame_tree_node_id();
+}
+
 const std::string& RenderFrameHostImpl::GetFrameName() {
   return frame_tree_node_->frame_name();
 }
 
 bool RenderFrameHostImpl::IsCrossProcessSubframe() {
   FrameTreeNode* parent_node = frame_tree_node_->parent();
   if (!parent_node)
     return false;
   return GetSiteInstance() !=
       parent_node->current_frame_host()->GetSiteInstance();
@@ skipping 1981 matching lines @@
             BrowserPluginInstanceIDToAXTreeID(value)));
         break;
       case AX_CONTENT_INT_ATTRIBUTE_LAST:
         NOTREACHED();
         break;
     }
   }
 }
 
 }  // namespace content