Move WebMouseEvent into its own header file.

third_party/WebKit/Source/platform/WebMouseEvent.cpp

 // Copyright 2016 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.
 
-#include "public/platform/WebInputEvent.h"
+#include "public/platform/WebMouseEvent.h"
 
 namespace blink {
 
 WebFloatPoint WebMouseEvent::movementInRootFrame() const {
   return WebFloatPoint((movementX / m_frameScale), (movementY / m_frameScale));
 }
 
 WebFloatPoint WebMouseEvent::positionInRootFrame() const {
   return WebFloatPoint((x / m_frameScale) + m_frameTranslate.x,
                        (y / m_frameScale) + m_frameTranslate.y);
 }
 
 void WebMouseEvent::flattenTransformSelf() {
   x = (x / m_frameScale) + m_frameTranslate.x;
   y = (y / m_frameScale) + m_frameTranslate.y;
   m_frameTranslate.x = 0;
   m_frameTranslate.y = 0;
   m_frameScale = 1;
 }
 
 }  // namespace blink