Sync part of the MouseEvent interface with CSSOM View

Source/core/events/MouseEvent.idl

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
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                                        [Default=Undefined] optional long screenY,
                                        [Default=Undefined] optional long clientX,
                                        [Default=Undefined] optional long clientY,
                                        [Default=Undefined] optional boolean ctrlKey,
                                        [Default=Undefined] optional boolean altKey,
                                        [Default=Undefined] optional boolean shiftKey,
                                        [Default=Undefined] optional boolean metaKey,
                                        [Default=Undefined] optional unsigned short button,
                                        [Default=Undefined] optional EventTarget? relatedTarget);
 
+    // CSSOM View Module
+    // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-mouseevent-interface
+    // TODO(philipj): These attributes should be of type double, and the spec
+    // also redefines screenX/Y and clientX/Y as double.
+    [MeasureAs=MouseEventX] readonly attribute long x;
+    [MeasureAs=MouseEventY] readonly attribute long y;
+    [MeasureAs=MouseEventOffsetX] readonly attribute long offsetX;
+    [MeasureAs=MouseEventOffsetY] readonly attribute long offsetY;
+
     // Pointer Lock
     // https://dvcs.w3.org/hg/pointerlock/raw-file/default/index.html#extensions-to-the-mouseevent-interface
     [MeasureAs=MouseEventMovementX] readonly attribute long movementX;
     [MeasureAs=MouseEventMovementY] readonly attribute long movementY;
 
     // Non-standard
-    [MeasureAs=MouseEventOffsetX] readonly attribute long offsetX;
-    [MeasureAs=MouseEventOffsetY] readonly attribute long offsetY;
-    [MeasureAs=MouseEventX] readonly attribute long x;
-    [MeasureAs=MouseEventY] readonly attribute long y;
     [MeasureAs=MouseEventFromElement] readonly attribute Node fromElement;
     [MeasureAs=MouseEventToElement] readonly attribute Node toElement;
     [MeasureAs=MouseEventWhich] readonly attribute long which;
     [DeprecateAs=PrefixedMouseEventMovementX, ImplementedAs=movementX] readonly attribute long webkitMovementX;
     [DeprecateAs=PrefixedMouseEventMovementY, ImplementedAs=movementY] readonly attribute long webkitMovementY;
 
     // FIXME: dataTransfer belongs on the DragEvent interface. crbug.com/498504
     readonly attribute DataTransfer dataTransfer;
 };