Refactoring the ownership of ui::InputMethod.

ui/views/ime/input_method_bridge.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/views/ime/input_method_bridge.h"
 
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/input_method_observer.h"
 #include "ui/events/event.h"
 #include "ui/gfx/geometry/rect.h"
@@ skipping 63 matching lines @@
   // this and go into |widget_|. NULL out |widget_| so we don't attempt to use
   // it.
   DetachFromWidget();
 
   // Host input method might have been destroyed at this point.
   if (host_)
     host_->DetachTextInputClient(this);
 }
 
 void InputMethodBridge::OnFocus() {
-  DCHECK(host_);
+  if (!host_)  // |host_| could be NULL after OnInputMethodDestroyed.
+    return;
 
   // Direct the shared IME to send TextInputClient messages to |this| object.
   if (shared_input_method_ || !host_->GetTextInputClient())
     host_->SetFocusedTextInputClient(this);
 
   // TODO(yusukes): We don't need to call OnTextInputTypeChanged() once we move
   // text input type tracker code to ui::InputMethodBase.
   if (GetFocusedView()) {
     OnTextInputTypeChanged(GetFocusedView());
     OnCaretBoundsChanged(GetFocusedView());
   }
 }
 
 void InputMethodBridge::OnBlur() {
-  DCHECK(host_);
+  if (!host_)  // |host_| could be NULL after OnInputMethodDestroyed.
+    return;
 
   if (HasCompositionText()) {
     ConfirmCompositionText();
     host_->CancelComposition(this);
   }
 
   if (host_->GetTextInputClient() == this)
     host_->SetFocusedTextInputClient(NULL);
 }
 
@@ skipping 234 matching lines @@
   OnTextInputTypeChanged(focused);
   OnCaretBoundsChanged(focused);
 }
 
 ui::InputMethod* InputMethodBridge::GetHostInputMethod() const {
   return host_;
 }
 
 
 }  // namespace views