Move WebMouseWheelEvent into its own header file.

content/common/input/input_event_stream_validator.cc

 // Copyright 2014 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 "content/common/input/input_event_stream_validator.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/public/common/content_switches.h"
+#include "third_party/WebKit/public/platform/WebGestureEvent.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "ui/events/blink/web_input_event_traits.h"
 
 using blink::WebInputEvent;
 using blink::WebGestureEvent;
 using blink::WebTouchEvent;
 
 namespace content {
 
 InputEventStreamValidator::InputEventStreamValidator()
@@ skipping 22 matching lines @@
     if (gesture.sourceDevice == blink::WebGestureDeviceTouchscreen)
       return gesture_validator_.Validate(gesture, error_msg);
   } else if (WebInputEvent::isTouchEventType(event.type)) {
     const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(event);
     return touch_validator_.Validate(touch, error_msg);
   }
   return true;
 }
 
 }  // namespace content