Move histograms and supporting code that don't belong in content out.

chrome/browser/ui/unload_controller.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 CHROME_BROWSER_UI_UNLOAD_CONTROLLER_H_
 #define CHROME_BROWSER_UI_UNLOAD_CONTROLLER_H_
 
 #include <set>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 23 matching lines @@
 //  2. WebContents notifies us via its delegate and BeforeUnloadFired()
 //     that the beforeunload handler was run. If the user allowed the
 //     close to continue, we detached the tab and hold onto it while the
 //     close finishes.
 //
 // Typical flow of closing a window:
 //  1. BrowserView::CanClose() calls TabsNeedBeforeUnloadFired().
 //     If beforeunload/unload handlers need to run, UnloadController returns
 //     true and calls ProcessPendingTabs() (private method).
 //  2. For each tab with a beforeunload/unload handler, ProcessPendingTabs()
-//        calls |web_contents->OnCloseStarted()|
+//        calls |CoreTabHelper::OnCloseStarted()|
 //        and   |web_contents->GetRenderViewHost()->FirePageBeforeUnload()|.
 //  3. If the user allowed the close to continue, we detach all the tabs with
 //     unload handlers, remove them from the tab strip, and finish closing
 //     the tabs in the background.
 //  4. The browser gets notified that the tab strip is empty and calls
 //     CloseFrame where the empty tab strip causes the window to hide.
 //     Once the detached tabs finish, the browser calls CloseFrame again and
 //     the window is finally closed.
 //
 class UnloadController : public content::NotificationObserver,
@@ skipping 116 matching lines @@
   scoped_ptr<DetachedWebContentsDelegate> detached_delegate_;
 
   base::WeakPtrFactory<UnloadController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UnloadController);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_UNLOAD_CONTROLLER_H_