Replaced synthetic MouseEvent in CustomButton::AcceleratorPressed() with just an Event.

ui/base/accelerators/accelerator.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.
 
 // This class describe a keyboard accelerator (or keyboard shortcut).
 // Keyboard accelerators are registered with the FocusManager.
 // It has a copy constructor and assignment operator so that it can be copied.
 // It also defines the < operator so that it can be used as a key in a std::map.
 //
 
@@ skipping 35 matching lines @@
               int modifiers,
               KeyState key_state = KeyState::PRESSED);
   explicit Accelerator(const KeyEvent& key_event);
   Accelerator(const Accelerator& accelerator);
   ~Accelerator();
 
   // Masks out all the non-modifiers KeyEvent |flags| and returns only the
   // available modifier ones. This does not include EF_IS_REPEAT.
   static int MaskOutKeyEventFlags(int flags);
 
+  KeyEvent ToKeyEvent() const;
+
   Accelerator& operator=(const Accelerator& accelerator);
 
   // Define the < operator so that the KeyboardShortcut can be used as a key in
   // a std::map.
   bool operator <(const Accelerator& rhs) const;
 
   bool operator ==(const Accelerator& rhs) const;
 
   bool operator !=(const Accelerator& rhs) const;
 
@@ skipping 64 matching lines @@
   virtual bool GetAcceleratorForCommandId(int command_id,
                                           Accelerator* accelerator) const = 0;
 
  protected:
   virtual ~AcceleratorProvider() {}
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_ACCELERATORS_ACCELERATOR_H_