Fix infinite loop in GetInputMethod.

chrome/browser/renderer_host/render_widget_host_view_views.cc

 // Copyright (c) 2011 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 "chrome/browser/renderer_host/render_widget_host_view_views.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 253 matching lines @@
 }
 
 void RenderWidgetHostViewViews::ImeUpdateTextInputState(
     ui::TextInputType type,
     bool can_compose_inline,
     const gfx::Rect& caret_rect) {
   // TODO(kinaba): currently, can_compose_inline is ignored and always treated
   // as true. We need to support "can_compose_inline=false" for PPAPI plugins
   // that may want to avoid drawing composition-text by themselves and pass
   // the responsibility to the browser.
-  DCHECK(GetInputMethod());
+
+  // This is async message and by the time the ipc arrived,
+  // RWHVV may be detached from Top level widget, in which case
+  // GetInputMethod may return NULL;
+  views::InputMethod* input_method = GetInputMethod();
+
   if (text_input_type_ != type) {
     text_input_type_ = type;
-    GetInputMethod()->OnTextInputTypeChanged(this);
+    if (input_method)
+      input_method->OnTextInputTypeChanged(this);
   }
   if (caret_bounds_ != caret_rect) {
     caret_bounds_ = caret_rect;
-    GetInputMethod()->OnCaretBoundsChanged(this);
+    if (input_method)
+      input_method->OnCaretBoundsChanged(this);
   }
 }
 
 void RenderWidgetHostViewViews::ImeCancelComposition() {
   DCHECK(GetInputMethod());
   GetInputMethod()->CancelComposition(this);
   has_composition_text_ = false;
 }
 
 void RenderWidgetHostViewViews::DidUpdateBackingStore(
@@ skipping 720 matching lines @@
 }
 #endif
 
 #if defined(USE_AURA)
 // static
 RenderWidgetHostView* RenderWidgetHostView::CreateViewForWidget(
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewViews(widget);
 }
 #endif