Revert r9953 since it caused regressions like:

chrome/views/widget_win.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_VIEWS_WIDGET_WIN_H_
 #define CHROME_VIEWS_WIDGET_WIN_H_
 
 #include <atlbase.h>
 #include <atlcrack.h>
 
@@ skipping 468 matching lines @@
   virtual void OnFinalMessage(HWND window);
 
   // Start tracking all mouse events so that this window gets sent mouse leave
   // messages too. |is_nonclient| is true when we should track WM_NCMOUSELEAVE
   // messages instead of WM_MOUSELEAVE ones.
   void TrackMouseEvents(DWORD mouse_tracking_flags);
 
   // Actually handle mouse events. These functions are called by subclasses who
   // override the message handlers above to do the actual real work of handling
   // the event in the View system.
-  bool ProcessMousePressed(const CPoint& point,
-                           UINT flags,
-                           bool dbl_click,
-                           bool non_client);
+  bool ProcessMousePressed(const CPoint& point, UINT flags, bool dbl_click);
   void ProcessMouseDragged(const CPoint& point, UINT flags);
   void ProcessMouseReleased(const CPoint& point, UINT flags);
   void ProcessMouseMoved(const CPoint& point, UINT flags, bool is_nonclient);
   void ProcessMouseExited();
 
   // Makes sure the window still fits on screen after a settings change message
   // from the OS, e.g. a screen resolution change.
   virtual void AdjustWindowToFitScreenSize();
 
   // Handles re-laying out content in response to a window size change.
@@ skipping 117 matching lines @@
   CComPtr<IAccessible> accessibility_root_;
 
   // Our hwnd.
   HWND hwnd_;
 };
 
 }  // namespace views
 
 #endif  // #ifndef CHROME_VIEWS_WIDGET_WIN_H_