Add a RWH_TabSwitchPaintDuration histogram.

chrome/browser/renderer_host/render_widget_host_view_mac.h

 // Copyright (c) 2006-2008 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_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/scoped_nsobject.h"
@@ skipping 122 matching lines @@
   bool about_to_validate_and_paint_;
 
   // This is the rectangle which we'll paint.
   NSRect invalid_rect_;
 
   // The time at which this view started displaying white pixels as a result of
   // not having anything to paint (empty backing store from renderer). This
   // value returns true for is_null() if we are not recording whiteout times.
   base::TimeTicks whiteout_start_time_;
 
+  // The time it took after this view was selected for it to be fully painted.
+  base::TimeTicks tab_switch_paint_time_;
+
   // Variables used by our implementaion of the NSTextInput protocol.
   // An input method of Mac calls the methods of this protocol not only to
   // notify an application of its status, but also to retrieve the status of
   // the application. That is, an application cannot control an input method
   // directly.
   // This object keeps the status of a composition of the renderer and returns
   // it when an input method asks for it.
   // We need to implement Objective-C methods for the NSTextInput protocol. On
   // the other hand, we need to implement a C++ method for an IPC-message
   // handler which receives input-method events from the renderer.
@@ skipping 57 matching lines @@
   // Factory used to safely scope delayed calls to ShutdownHost().
   ScopedRunnableMethodFactory<RenderWidgetHostViewMac> shutdown_factory_;
 
   // Used for positioning a popup menu.
   BaseView* parent_view_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_