Use FrameTreeNode ID as frameId in extension APIs

extensions/renderer/resources/messaging.js

 // Copyright 2014 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.
 
 // chrome.runtime.messaging API implementation.
 
   // TODO(kalman): factor requiring chrome out of here.
   var chrome = requireNative('chrome').GetChrome();
   var Event = require('event_bindings').Event;
   var lastError = require('lastError');
@@ skipping 58 matching lines @@
   PortImpl.prototype.disconnect = function() {
     messagingNatives.CloseChannel(this.portId_, true);
     this.destroy_();
   };
 
   PortImpl.prototype.destroy_ = function() {
     if (this.onDestroy_)
       this.onDestroy_();
     privates(this.onDisconnect).impl.destroy_();
     privates(this.onMessage).impl.destroy_();
+    // TODO(robwu): Remove port lifetime management because it is completely
+    // handled in the browser. The renderer's only roles are
+    // 1) rejecting ports so that the browser knows that the renderer is not
+    //    interested in the port (this is merely an optimization)
+    // 2) acknowledging port creations, so that the browser knows that the port
+    //    was successfully created (from the perspective of the extension), but
+    //    then closed for some non-fatal reason.
+    // 3) notifying the browser of explicit port closure via .disconnect().
+    // In other cases (navigations), the browser automatically cleans up the
+    //    port.
     messagingNatives.PortRelease(this.portId_);
     delete ports[this.portId_];
   };
 
   // Returns true if the specified port id is in this context. This is used by
   // the C++ to avoid creating the javascript message for all the contexts that
   // don't care about a particular message.
   function hasPort(portId) {
     return portId in ports;
   };
@@ skipping 294 matching lines @@
 exports.$set('Port', Port);
 exports.$set('createPort', createPort);
 exports.$set('sendMessageImpl', sendMessageImpl);
 exports.$set('sendMessageUpdateArguments', sendMessageUpdateArguments);
 
 // For C++ code to call.
 exports.$set('hasPort', hasPort);
 exports.$set('dispatchOnConnect', dispatchOnConnect);
 exports.$set('dispatchOnDisconnect', dispatchOnDisconnect);
 exports.$set('dispatchOnMessage', dispatchOnMessage);