Makes sure that an input method doesn't reference to a destroyed object.

ui/base/ime/mock_input_method.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 "ui/base/ime/mock_input_method.h"
 
 namespace ui {
 
 MockInputMethod::MockInputMethod(internal::InputMethodDelegate* delegate)
     : text_input_client_(NULL) {
 }
 
 MockInputMethod::~MockInputMethod() {
 }
 
 void MockInputMethod::SetDelegate(internal::InputMethodDelegate* delegate) {
 }
 
 void MockInputMethod::SetFocusedTextInputClient(TextInputClient* client) {
   if (text_input_client_ == client)
     return;
   text_input_client_ = client;
   if (client)
     OnTextInputTypeChanged(client);
 }
 
+void MockInputMethod::DetachTextInputClient(TextInputClient* client) {
+  if (text_input_client_ == client)
+    text_input_client_ = NULL;
+}
+
 TextInputClient* MockInputMethod::GetTextInputClient() const {
   return text_input_client_;
 }
 
 bool MockInputMethod::DispatchKeyEvent(const base::NativeEvent& native_event) {
   return false;
 }
 
 bool MockInputMethod::DispatchFabricatedKeyEvent(const ui::KeyEvent& event) {
   return false;
@@ skipping 64 matching lines @@
 
 void MockInputMethod::AddObserver(InputMethodObserver* observer) {
   observer_list_.AddObserver(static_cast<Observer*>(observer));
 }
 
 void MockInputMethod::RemoveObserver(InputMethodObserver* observer) {
   observer_list_.RemoveObserver(static_cast<Observer*>(observer));
 }
 
 }  // namespace ui