[Media Router] Add UMA metrics for Media Router Dialog WebUI performance.

chrome/browser/ui/webui/media_router/media_router_webui_message_handler.h

 // Copyright 2015 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 CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_
 
 #include <vector>
 
 #include "base/macros.h"
@@ skipping 41 matching lines @@
   // Handlers for JavaScript messages.
   // In all cases, |args| consists of a single DictionaryValue containing the
   // actual parameters.
   // See media_router_ui_interface.js for documentation on parameters.
   void OnRequestInitialData(const base::ListValue* args);
   void OnCreateRoute(const base::ListValue* args);
   void OnActOnIssue(const base::ListValue* args);
   void OnCloseRoute(const base::ListValue* args);
   void OnCloseDialog(const base::ListValue* args);
   void OnReportSinkCount(const base::ListValue* args);
+  void OnInitialDataReceived(const base::ListValue* args);
 
   // Performs an action for an Issue of |type|.
   // |args| contains additional parameter that varies based on |type|.
   // Returns |true| if the action was successfully performed.
   bool ActOnIssueType(const IssueAction::Type& type,
                       const base::DictionaryValue* args);
 
   // Keeps track of whether a command to close the dialog has been issued.
   bool dialog_closing_;
 
   MediaRouterUI* media_router_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterWebUIMessageHandler);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_WEBUI_MESSAGE_HANDLER_H_