Fixed crash in accessibility code in LegacyRenderWidgetHost.

content/browser/renderer_host/legacy_render_widget_host_win.cc

 // Copyright (c) 2014 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 "content/browser/renderer_host/legacy_render_widget_host_win.h"
 
 #include <objbase.h>
 
 #include <memory>
 
@@ skipping 164 matching lines @@
     return static_cast<LRESULT>(0L);
 
   RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(
       host_->GetRenderWidgetHost());
   if (!rwhi)
     return static_cast<LRESULT>(0L);
 
   BrowserAccessibilityManagerWin* manager =
       static_cast<BrowserAccessibilityManagerWin*>(
           rwhi->GetRootBrowserAccessibilityManager());
-  if (!manager)
+  if (!manager || !manager->GetRoot())
     return static_cast<LRESULT>(0L);
 
   base::win::ScopedComPtr<IAccessible> root(
       ToBrowserAccessibilityWin(manager->GetRoot())->GetCOM());
   return LresultFromObject(IID_IAccessible, w_param,
       static_cast<IAccessible*>(root.Detach()));
 }
 
 // We send keyboard/mouse/touch messages to the parent window via SendMessage.
 // While this works, this has the side effect of converting input messages into
@@ skipping 226 matching lines @@
       direct_manipulation_helper_->Activate(hwnd());
     } else if (window_pos->flags & SWP_HIDEWINDOW) {
       direct_manipulation_helper_->Deactivate(hwnd());
     }
   }
   SetMsgHandled(FALSE);
   return 0;
 }
 
 }  // namespace content