Add POINTER_WHEEL_CHANGED event to mojo.

ui/events/event.h

 // Copyright (c) 2012 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 UI_EVENTS_EVENT_H_
 #define UI_EVENTS_EVENT_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 441 matching lines @@
   // of kWheelDelta.
   // Note: offset_.x() > 0/offset_.y() > 0 means scroll left/up.
   gfx::Vector2d offset;
 };
 
 class EVENTS_EXPORT MouseEvent : public LocatedEvent {
  public:
   explicit MouseEvent(const base::NativeEvent& native_event);
 
   // |pointer_event.IsMousePointerEvent()| must be true.
+  // Note: If |pointer_event| is a mouse wheel pointer event, use the
+  // MouseWheelEvent version of this function to convert to a MouseWheelEvent
+  // instead.
   explicit MouseEvent(const PointerEvent& pointer_event);
 
   // Create a new MouseEvent based on the provided model.
   // Uses the provided |type| and |flags| for the new event.
   // If source / target windows are provided, the model location will be
   // converted from |source| coordinate system to |target| coordinate system.
   template <class T>
   MouseEvent(const MouseEvent& model, T* source, T* target)
       : LocatedEvent(model, source, target),
         changed_button_flags_(model.changed_button_flags_),
@@ skipping 112 matching lines @@
 
 class ScrollEvent;
 
 class EVENTS_EXPORT MouseWheelEvent : public MouseEvent {
  public:
   // See |offset| for details.
   static const int kWheelDelta;
 
   explicit MouseWheelEvent(const base::NativeEvent& native_event);
   explicit MouseWheelEvent(const ScrollEvent& scroll_event);
+  explicit MouseWheelEvent(const PointerEvent& pointer_event);
   MouseWheelEvent(const MouseEvent& mouse_event, int x_offset, int y_offset);
   MouseWheelEvent(const MouseWheelEvent& mouse_wheel_event);
 
   template <class T>
   MouseWheelEvent(const MouseWheelEvent& model,
                   T* source,
                   T* target)
       : MouseEvent(model, source, target, model.type(), model.flags()),
         offset_(model.x_offset(), model.y_offset()) {
   }
@@ skipping 413 matching lines @@
   // dispatched. This field gets a non-zero value only for gestures that are
   // released through TouchDispositionGestureFilter::SendGesture. The gesture
   // events that aren't fired directly in response to processing a touch-event
   // (e.g. timer fired ones), this id is zero. See crbug.com/618738.
   uint32_t unique_touch_event_id_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_H_