Remove WindowDelegate::OnRequestClose().

ui/aura/window_delegate.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_AURA_WINDOW_DELEGATE_H_
 #define UI_AURA_WINDOW_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "ui/aura/aura_export.h"
@@ skipping 76 matching lines @@
   // Called from Window::HitTest to check if the window has a custom hit test
   // mask. It works similar to the views counterparts. That is, if the function
   // returns true, GetHitTestMask below will be called to get the mask.
   // Otherwise, Window will hit-test against its bounds.
   virtual bool HasHitTestMask() const = 0;
 
   // Called from Window::HitTest to retrieve hit test mask when HasHitTestMask
   // above returns true.
   virtual void GetHitTestMask(gfx::Path* mask) const = 0;
 
-  // Sent when the server requests the window to close.
-  virtual void OnRequestClose();
-
  protected:
   ~WindowDelegate() override {}
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_DELEGATE_H_