Add POINTER_WHEEL_CHANGED event to mojo.

ui/events/mojo/event_constants.mojom

 // 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.
 
 module ui.mojom;
 
 // AcceleratorPhase specifies which phase of event matching the matcher should
 // be considered for. See WindowTree for details on how it handles the
 // AcceleratorPhase.
 enum AcceleratorPhase {
   PRE_TARGET,
   POST_TARGET,
 };
 
 enum EventType {
   UNKNOWN,
   KEY_PRESSED,
   KEY_RELEASED,
   POINTER_CANCEL,
   POINTER_DOWN,
   POINTER_MOVE,
   POINTER_UP,
+  POINTER_WHEEL_CHANGED,
   MOUSE_EXIT,
-  WHEEL,
 };
 
 // This mirrors ui::EventFlags
 // TODO(morrita): Use shift operator once it is available.
 const int32 kEventFlagNone               = 0x00000;
 const int32 kEventFlagIsSynthesized      = 0x00001;
 const int32 kEventFlagShiftDown          = 0x00002;
 const int32 kEventFlagControlDown        = 0x00004;
 const int32 kEventFlagAltDown            = 0x00008;
 const int32 kEventFlagCommandDown        = 0x00010;
@@ skipping 19 matching lines @@
   PEN,
   TOUCH,
 };
 
 enum WheelMode {
   PIXEL,
   LINE,
   PAGE,
   SCALING,
 };