Fully support the autohide shelf option for touch UI on Windows.

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 31 matching lines @@
   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 TAP_UP gesture if the
   // finger(s) were moving quickly before they are released.
   ET_GESTURE_MULTIFINGER_SWIPE,
   ET_GESTURE_SHOW_PRESS,
 
+  // Sent by Win8+ metro when the user swipes from the bottom or top.
+  ET_GESTURE_WIN8_EDGE_SWIPE,
+
   // Scroll support.
   // TODO[davemoore] we need to unify these events w/ touch and gestures.
   ET_SCROLL,
   ET_SCROLL_FLING_START,
   ET_SCROLL_FLING_CANCEL,
 
   // Sent by the system to indicate any modal type operations, such as drag and
   // drop or menus, should stop.
   ET_CANCEL_MODE,
 
@@ skipping 46 matching lines @@
   EP_PREDISPATCH,
   EP_PRETARGET,
   EP_TARGET,
   EP_POSTTARGET,
   EP_POSTDISPATCH
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_CONSTANTS_H_