Fixs bug resulting in double event delivery in mus

ui/views/test/platform_test_helper.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 UI_VIEWS_TEST_PLATFORM_TEST_HELPER_H_
 #define UI_VIEWS_TEST_PLATFORM_TEST_HELPER_H_
 
 #include <memory>
 
 #include "base/callback_forward.h"
@@ skipping 16 matching lines @@
   static void SetIsMus();
   static bool IsMus();
 
   // Called once the ViewsTestHelper has been created, but before SetUp() is
   // called.
   virtual void OnTestHelperCreated(ViewsTestHelper* helper) {}
 
   // Simulate an OS-level destruction of the native window held by |widget|.
   virtual void SimulateNativeDestroy(Widget* widget);
 
+  virtual void DisableMusInputMethod(Widget* widget) {}
+
  private:
   DISALLOW_COPY_AND_ASSIGN(PlatformTestHelper);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_TEST_PLATFORM_TEST_HELPER_H_