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

ash/wm/gestures/shelf_gesture_handler.cc

 // 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.
 
 #include "ash/wm/gestures/shelf_gesture_handler.h"
 
 #include "ash/root_window_controller.h"
 #include "ash/session_state_delegate.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_types.h"
@@ skipping 25 matching lines @@
       shell->session_state_delegate()->IsScreenLocked()) {
     // The gestures are disabled in the lock/login screen.
     return false;
   }
 
   // TODO(oshima): Find the root window controller from event's location.
   RootWindowController* controller = Shell::GetPrimaryRootWindowController();
 
   ShelfLayoutManager* shelf = controller->GetShelfLayoutManager();
 
+#if defined(OS_WIN)

[sky, 2014/02/11 18:55:22]

Is there a reason we need the ifdefs here and in the test? The events won't be
generated other than win8, but it should be fine to test, right?

+  if (event.type() == ui::ET_GESTURE_WIN8_EDGE_SWIPE) {
+    shelf->OnGestureEdgeSwipe(event);
+    return true;
+  }
+#endif
+
   const aura::Window* fullscreen = controller->GetWindowForFullscreenMode();
   if (fullscreen &&
       ash::wm::GetWindowState(fullscreen)->hide_shelf_when_fullscreen()) {
     return false;
   }
 
   if (event.type() == ui::ET_GESTURE_SCROLL_BEGIN) {
     drag_in_progress_ = true;
     shelf->StartGestureDrag(event);
     return true;
@@ skipping 27 matching lines @@
     return true;
   }
 
   // Unexpected event. Reset the state and let the event fall through.
   shelf->CancelGestureDrag();
   return false;
 }
 
 }  // namespace internal
 }  // namespace ash