Move WebMouseWheelEvent into its own header file.

content/browser/renderer_host/input/touch_emulator.h

 // 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_
 #define CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/browser/renderer_host/input/touch_emulator_client.h"
 #include "content/common/cursors/webcursor.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
 #include "ui/events/gesture_detection/filtered_gesture_provider.h"
 #include "ui/events/gesture_detection/gesture_provider_config_helper.h"
 #include "ui/gfx/geometry/size_f.h"
 
+namespace blink {
+class WebMouseWheelEvent;
+}
+
 namespace content {
 
 // Emulates touch input with mouse and keyboard.
 class CONTENT_EXPORT TouchEmulator : public ui::GestureProviderClient {
  public:
   TouchEmulator(TouchEmulatorClient* client, float device_scale_factor);
   ~TouchEmulator() override;
 
   void Enable(ui::GestureProviderConfigType config_type);
   void Disable();
@@ skipping 91 matching lines @@
   // The cumulative scale change from the start of pinch gesture.
   float pinch_scale_;
   bool pinch_gesture_active_;
 
   DISALLOW_COPY_AND_ASSIGN(TouchEmulator);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_INPUT_TOUCH_EMULATOR_H_