Add UMA histograms to MHTML save operations.

content/browser/frame_host/render_frame_host_impl.h

 // 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.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 695 matching lines @@
   void OnAccessibilitySnapshotResponse(
       int callback_id,
       const AXContentTreeUpdate& snapshot);
   void OnToggleFullscreen(bool enter_fullscreen);
   void OnDidStartLoading(bool to_different_document);
   void OnDidStopLoading();
   void OnDidChangeLoadProgress(double load_progress);
   void OnSerializeAsMHTMLResponse(
       int job_id,
       bool success,
-      const std::set<std::string>& digests_of_uris_of_serialized_resources);
+      const std::set<std::string>& digests_of_uris_of_serialized_resources,
+      base::TimeDelta renderer_main_thread_time);
 
 #if defined(USE_EXTERNAL_POPUP_MENU)
   void OnShowPopup(const FrameHostMsg_ShowPopup_Params& params);
   void OnHidePopup();
 #endif
 
   // Registers Mojo interfaces that this frame host makes available.
   void RegisterMojoInterfaces();
 
   // Resets any waiting state of this RenderFrameHost that is no longer
@@ skipping 326 matching lines @@
 
   // NOTE: This must be the last member.
   base::WeakPtrFactory<RenderFrameHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_