Make WebPluginContainerImpl::invalidateRect check for NULL renderer

Source/web/WebPluginContainerImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 118 matching lines @@
 
     gc->restore();
 }
 
 void WebPluginContainerImpl::invalidateRect(const IntRect& rect)
 {
     if (!parent())
         return;
 
     RenderBox* renderer = toRenderBox(m_element->renderer());
+    if (!renderer)
+        return;
 
     IntRect dirtyRect = rect;
     dirtyRect.move(renderer->borderLeft() + renderer->paddingLeft(),
                    renderer->borderTop() + renderer->paddingTop());
 
     // For querying RenderLayer::compositingState().
     // This code should be correct.
     DisableCompositingQueryAsserts disabler;
     renderer->invalidatePaintRectangle(dirtyRect);
 }
@@ skipping 824 matching lines @@
 
     return clipRect;
 }
 
 bool WebPluginContainerImpl::pluginShouldPersist() const
 {
     return m_webPlugin->shouldPersist();
 }
 
 } // namespace blink