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

ui/base/ime/input_method.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 UI_BASE_IME_INPUT_METHOD_H_
 #define UI_BASE_IME_INPUT_METHOD_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 65 matching lines @@
   // translated into other predefined event callbacks. Currently this method is
   // used only for IME functionalities specific to Windows.
   // TODO(ime): Break down these messages into platform-neutral methods.
   virtual bool OnUntranslatedIMEMessage(const base::NativeEvent& event,
                                         NativeEventResult* result) = 0;
 
   // Sets the text input client which receives text input events such as
   // SetCompositionText(). |client| can be NULL. A gfx::NativeWindow which
   // implementes TextInputClient interface, e.g. NWA and RWHVA, should register
   // itself by calling the method when it is focused, and unregister itself by
-  // calling the metho with NULL when it is unfocused.
+  // calling the method with NULL when it is unfocused.
   virtual void SetFocusedTextInputClient(TextInputClient* client) = 0;
 
+  // Detaches and forgets the |client| regardless of whether it has the focus or
+  // not.  This method is meant to be called when the |client| is going to be
+  // destroyed.
+  virtual void DetachTextInputClient(TextInputClient* client) = 0;
+
   // Gets the current text input client. Returns NULL when no client is set.
   virtual TextInputClient* GetTextInputClient() const = 0;
 
   // Dispatches a key event to the input method. The key event will be
   // dispatched back to the caller via
   // ui::InputMethodDelegate::DispatchKeyEventPostIME(), once it's processed by
   // the input method. It should only be called by a message dispatcher.
   // Returns true if the event was processed.
   virtual bool DispatchKeyEvent(const base::NativeEvent& native_key_event) = 0;
 
@@ skipping 63 matching lines @@
   virtual bool IsCandidatePopupOpen() const = 0;
 
   // Management of the observer list.
   virtual void AddObserver(InputMethodObserver* observer) = 0;
   virtual void RemoveObserver(InputMethodObserver* observer) = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_IME_INPUT_METHOD_H_