Revert r9953 since it caused regressions like:

chrome/views/event.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_EVENT_H__
 #define CHROME_VIEWS_EVENT_H__
 
 #include "base/basictypes.h"
 #include "base/gfx/point.h"
 #include "webkit/glue/window_open_disposition.h"
@@ skipping 138 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 //
 // MouseEvent class
 //
 // A mouse event is used for any input event related to the mouse.
 //
 ////////////////////////////////////////////////////////////////////////////////
 class MouseEvent : public LocatedEvent {
  public:
   // Flags specific to mouse events
-  enum MouseEventFlags {
-    EF_IS_DOUBLE_CLICK = 1 << 16,
-    EF_IS_NON_CLIENT = 1 << 17
-  };
+  enum MouseEventFlags { EF_IS_DOUBLE_CLICK = 1 << 16 };
 
   // Create a new mouse event
   MouseEvent(EventType type, int x, int y, int flags)
       : LocatedEvent(type, gfx::Point(x, y), flags) {
   }
 
   // Create a new mouse event from a type and a point. If from / to views
   // are provided, the point will be converted from 'from' coordinate system to
   // 'to' coordinate system.
   MouseEvent(EventType type,
@@ skipping 131 matching lines @@
   const OSExchangeData& data_;
   int source_operations_;
 
   DISALLOW_EVIL_CONSTRUCTORS(DropTargetEvent);
 };
 
 }  // namespace views
 
 #endif  // CHROME_VIEWS_EVENT_H__