Add UMA for first app list paint on Windows.

ui/app_list/views/app_list_view.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 UI_APP_LIST_VIEWS_APP_LIST_VIEW_H_
 #define UI_APP_LIST_VIEWS_APP_LIST_VIEW_H_
 
+#include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "ui/app_list/app_list_export.h"
 #include "ui/app_list/app_list_model_observer.h"
 #include "ui/views/bubble/bubble_delegate.h"
 
 namespace views {
 class Widget;
 }
 
@@ skipping 42 matching lines @@
   // Shows the UI when there are no pending icon loads. Otherwise, starts a
   // timer to show the UI when a maximum allowed wait time has expired.
   void ShowWhenReady();
 
   void Close();
 
   void UpdateBounds();
 
   // Overridden from views::View:
   virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual void Paint(gfx::Canvas* canvas) OVERRIDE;
 
   // WidgetDelegate overrides:
   virtual bool ShouldHandleSystemCommands() const OVERRIDE;
 
   void Prerender();
 
   // Invoked when the sign-in status is changed to switch on/off sign-in view.
   void OnSigninStatusChanged();
 
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
+  // Set a callback to be called the next time any app list paints.
+  static void SetNextPaintCallback(const base::Closure& callback);
+
 #if defined(OS_WIN)
   HWND GetHWND() const;
 #endif
 
  private:
   // Overridden from views::WidgetDelegateView:
   virtual views::View* GetInitiallyFocusedView() OVERRIDE;
   virtual gfx::ImageSkia GetWindowIcon() OVERRIDE;
   virtual bool WidgetHasHitTestMask() const OVERRIDE;
   virtual void GetWidgetHitTestMask(gfx::Path* mask) const OVERRIDE;
@@ skipping 22 matching lines @@
   SigninView* signin_view_;
 
   ObserverList<Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_APP_LIST_VIEW_H_