Move WebMouseWheelEvent into its own header file.

ui/events/blink/blink_event_util.cc

 // Copyright 2015 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/blink/blink_event_util.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <bitset>
 #include <cmath>
 #include <limits>
 
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
+#include "third_party/WebKit/public/platform/WebMouseWheelEvent.h"
 #include "ui/events/base_event_utils.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/gesture_detection/gesture_event_data.h"
 #include "ui/events/gesture_detection/motion_event.h"
 #include "ui/events/gesture_event_details.h"
 #include "ui/events/keycodes/dom/keycode_converter.h"
 #include "ui/gfx/geometry/safe_integer_conversions.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/transform.h"
 
@@ skipping 931 matching lines @@
   switch (type) {
     case blink::WebGestureEvent::GestureScrollUpdate:
     case blink::WebGestureEvent::GesturePinchUpdate:
       return true;
     default:
       return false;
   }
 }
 
 }  // namespace ui