Fix crash on extension IME reloading on Linux Desktop with chromeos=1.

chromeos/dbus/ibus/ibus_engine_service.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 CHROMEOS_DBUS_IBUS_IBUS_ENGINE_SERVICE_H_
 #define CHROMEOS_DBUS_IBUS_IBUS_ENGINE_SERVICE_H_
 
 #include <string>
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 98 matching lines @@
     IBUS_ENGINE_PREEEDIT_FOCUS_OUT_MODE_CLEAR = 0,
     IBUS_ENGINE_PREEEDIT_FOCUS_OUT_MODE_COMMIT = 1,
   };
 
   virtual ~IBusEngineService();
 
   // Sets a new IBus engine handler and old handler will be overridden.
   // This class doesn't take the ownership of |handler|.
   virtual void SetEngine(IBusEngineHandlerInterface* handler) = 0;
 
-  // Unsets the current IBus engine handler.
-  virtual void UnsetEngine() = 0;
+  // Unsets the IBus engine handler if |handler| equals to current engine
+  // handler.
+  virtual void UnsetEngine(IBusEngineHandlerInterface* handler) = 0;
 
   // Emits RegisterProperties signal.
   virtual void RegisterProperties(
       const IBusPropertyList& property_list) = 0;
   // Emits UpdatePreedit signal.
   virtual void UpdatePreedit(const IBusText& ibus_text,
                              uint32 cursor_pos,
                              bool is_visible,
                              IBusEnginePreeditFocusOutMode mode) = 0;
   // Emits UpdateAuxiliaryText signal.
@@ skipping 22 matching lines @@
   // Create() should be used instead.
   IBusEngineService();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(IBusEngineService);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_IBUS_IBUS_ENGINE_SERVICE_H_