Prepare for Unified Gesture Recognizer landing in Aura

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 20 matching lines @@
   // GestureEvent types
   ET_GESTURE_SCROLL_BEGIN,
   ET_GESTURE_TYPE_START = ET_GESTURE_SCROLL_BEGIN,
   ET_GESTURE_SCROLL_END,
   ET_GESTURE_SCROLL_UPDATE,
   ET_GESTURE_TAP,
   ET_GESTURE_TAP_DOWN,
   ET_GESTURE_TAP_CANCEL,
   ET_GESTURE_TAP_UNCONFIRMED, // User tapped, but the tap delay hasn't expired.
   ET_GESTURE_DOUBLE_TAP,
-  ET_GESTURE_BEGIN,  // Sent before any other gesture types.
-  ET_GESTURE_END,    // Sent after any other gestures.
+  ET_GESTURE_BEGIN,  // The first event sent when each finger is pressed.
+  ET_GESTURE_END,    // Sent for each released finger.
   ET_GESTURE_TWO_FINGER_TAP,
   ET_GESTURE_PINCH_BEGIN,
   ET_GESTURE_PINCH_END,
   ET_GESTURE_PINCH_UPDATE,
   ET_GESTURE_LONG_PRESS,
   ET_GESTURE_LONG_TAP,
   // A SWIPE gesture can happen at the end of a touch sequence involving one or
   // more fingers if the finger velocity was high enough when the first finger
   // was released.
   ET_GESTURE_SWIPE,
@@ skipping 75 matching lines @@
   EP_PREDISPATCH,
   EP_PRETARGET,
   EP_TARGET,
   EP_POSTTARGET,
   EP_POSTDISPATCH
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_CONSTANTS_H_