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

chromeos/dbus/ibus/ibus_engine_service.cc

 // 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.
 
 #include "chromeos/dbus/ibus/ibus_engine_service.h"
 
 #include <string>
 #include "base/bind.h"
 #include "base/callback.h"
 #include "chromeos/dbus/ibus/ibus_constants.h"
@@ skipping 124 matching lines @@
 
   // IBusEngineService override.
   virtual void SetEngine(IBusEngineHandlerInterface* handler) OVERRIDE {
     DVLOG_IF(1, engine_handler_ != NULL) << "Replace engine.";
     if (engine_handler_)
       engine_handler_->Disable();
     engine_handler_ = handler;
   }
 
   // IBusEngineService override.
-  virtual void UnsetEngine() OVERRIDE {
-    LOG_IF(ERROR, engine_handler_ == NULL) << "There is no engine.";
-    engine_handler_ = NULL;
+  virtual void UnsetEngine(IBusEngineHandlerInterface* handler) OVERRIDE {
+    if (engine_handler_ == handler)
+      engine_handler_ = NULL;
   }
 
   // IBusEngineService override.
   virtual void RegisterProperties(
       const IBusPropertyList& property_list) OVERRIDE {
     dbus::Signal signal(ibus::engine::kServiceInterface,
                         ibus::engine::kRegisterPropertiesSignal);
     dbus::MessageWriter writer(&signal);
     AppendIBusPropertyList(property_list, &writer);
     exported_object_->SendSignal(&signal);
@@ skipping 321 matching lines @@
  public:
   IBusEngineServiceDaemonlessImpl() {}
   virtual ~IBusEngineServiceDaemonlessImpl() {}
 
   // IBusEngineService override.
   virtual void SetEngine(IBusEngineHandlerInterface* handler) OVERRIDE {
     IBusBridge::Get()->SetEngineHandler(handler);
   }
 
   // IBusEngineService override.
-  virtual void UnsetEngine() OVERRIDE {
-    IBusBridge::Get()->SetEngineHandler(NULL);
+  virtual void UnsetEngine(IBusEngineHandlerInterface* handler) OVERRIDE {
+    if (IBusBridge::Get()->GetEngineHandler() == handler)
+      IBusBridge::Get()->SetEngineHandler(NULL);
   }
 
   // IBusEngineService override.
   virtual void RegisterProperties(
       const IBusPropertyList& property_list) OVERRIDE {
     IBusPanelPropertyHandlerInterface* property =
         IBusBridge::Get()->GetPropertyHandler();
     if (property)
       property->RegisterProperties(property_list);
   }
@@ skipping 75 matching lines @@
     DBusClientImplementationType type,
     dbus::Bus* bus,
     const dbus::ObjectPath& object_path) {
   if (type == REAL_DBUS_CLIENT_IMPLEMENTATION)
     return new IBusEngineServiceImpl(bus, object_path);
   else
     return new IBusEngineServiceDaemonlessImpl();
 }
 
 }  // namespace chromeos