exo: Fix dragging edge cases

components/exo/wm_helper_ash.h

 // Copyright 2016 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 COMPONENTS_EXO_WM_HELPER_ASH_H_
 #define COMPONENTS_EXO_WM_HELPER_ASH_H_
 
 #include "ash/common/shell_observer.h"
 #include "ash/common/system/accessibility_observer.h"
 #include "base/macros.h"
@@ skipping 45 matching lines @@
   void OnCursorVisibilityChanged(bool is_visible) override;
   void OnCursorSetChanged(ui::CursorSetType cursor_set) override;
 
   // Overridden from ash::AccessibilityObserver:
   void OnAccessibilityModeChanged(
       ash::AccessibilityNotificationVisibility notify) override;
 
   // Overriden from ash::ShellObserver:
   void OnMaximizeModeStarted() override;
   void OnMaximizeModeEnded() override;
+  void OnOverviewModeStarting() override;
+  void OnOverviewModeEnded() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WMHelperAsh);
 };
 
 }  // namespace exo
 
 #endif  // COMPONENTS_EXO_WM_HELPER_H_