MacViews: Send Mac scrollWheel NSEvents as ui::ET_SCROLL (ui::ScrollEvent).

ui/events/event_constants.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_CONSTANTS_H_
 #define UI_EVENTS_EVENT_CONSTANTS_H_
 
 namespace ui {
 
 // Event types. (prefixed because of a conflict with windows headers)
@@ skipping 146 matching lines @@
 
 // Phase of the event dispatch.
 enum EventPhase {
   EP_PREDISPATCH,
   EP_PRETARGET,
   EP_TARGET,
   EP_POSTTARGET,
   EP_POSTDISPATCH
 };
 
+// Momentum phase information used for a ScrollEvent.
+enum class EventMomentumPhase {
+  // Event is a non-momentum update to an event stream already begun.
+  NONE,
+
+  // Event is the beginning of an event stream that may result in momentum.
+  MAY_BEGIN,
+
+  // Event is an update while in a momentum phase. A "begin" event for the
+  // momentum phase portion of an event stream uses this also, but the scroll
+  // offsets will be zero.
+  INERTIAL_UPDATE,
+
+  // Event marks the end of the current event stream. Note that this is also set
+  // for events that are not a "stream", but indicate both the start and end of
+  // the event (e.g. a mouse wheel tick).
+  END,
+};
+
 // Device ID for Touch and Key Events.
 enum EventDeviceId {
   ED_UNKNOWN_DEVICE = -1
 };
 
 // Pointing device type.
 enum class EventPointerType : int {
   POINTER_TYPE_UNKNOWN = 0,
   POINTER_TYPE_MOUSE,
   POINTER_TYPE_PEN,
   POINTER_TYPE_TOUCH,
   POINTER_TYPE_ERASER,
 };
 
 // Device type for gesture events.
 enum class GestureDeviceType : int {
   DEVICE_UNKNOWN = 0,
   DEVICE_TOUCHPAD,
   DEVICE_TOUCHSCREEN,
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_CONSTANTS_H_