Add UMA to measure potential impact of Fast Tab Close.

content/browser/web_contents/render_view_host_manager.h

 // 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.
 
 #ifndef CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_
 #define CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 41 matching lines @@
     // corresponding to this view host. If this method is not called and the
     // process is not shared, then the WebContentsImpl will act as though the
     // renderer is not running (i.e., it will render "sad tab"). This method is
     // automatically called from LoadURL.
     //
     // If you are attaching to an already-existing RenderView, you should call
     // InitWithExistingID.
     virtual bool CreateRenderViewForRenderManager(
         content::RenderViewHost* render_view_host, int opener_route_id) = 0;
     virtual void BeforeUnloadFiredFromRenderManager(
-        bool proceed, bool* proceed_to_fire_unload) = 0;
+        bool proceed, const base::TimeTicks& proceed_time,
+        bool* proceed_to_fire_unload) = 0;
     virtual void RenderViewGoneFromRenderManager(
         content::RenderViewHost* render_view_host) = 0;
     virtual void UpdateRenderViewSizeForRenderManager() = 0;
     virtual void NotifySwappedFromRenderManager() = 0;
     virtual NavigationControllerImpl& GetControllerForRenderManager() = 0;
 
     // Create swapped out RenderViews in the given SiteInstance for each tab in
     // the opener chain of this tab, if any.  This allows the current tab to
     // make cross-process script calls to its opener(s).  Returns the route ID
     // of the immediate opener, if one exists (otherwise MSG_ROUTING_NONE).
@@ skipping 247 matching lines @@
   // The intersitial page currently shown if any, not own by this class
   // (the InterstitialPage is self-owned, it deletes itself when hidden).
   InterstitialPageImpl* interstitial_page_;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostManager);
 };
 
 #endif  // CONTENT_BROWSER_WEB_CONTENTS_RENDER_VIEW_HOST_MANAGER_H_