Check for guest renderer before casting to RenderWidgetHostViewAura in

content/browser/web_contents/web_contents_view_aura.cc

Index: content/browser/web_contents/web_contents_view_aura.cc
diff --git a/content/browser/web_contents/web_contents_view_aura.cc b/content/browser/web_contents/web_contents_view_aura.cc
index 582d47335df6b639630fda8a4c6b8ad56ea56c21..2446151fbe74df05ec38b847cde74acee719ea8d 100644
--- a/content/browser/web_contents/web_contents_view_aura.cc
+++ b/content/browser/web_contents/web_contents_view_aura.cc
@@ -97,8 +97,12 @@ bool ShouldNavigateBack(const NavigationController& controller,
 
 RenderWidgetHostViewAura* ToRenderWidgetHostViewAura(
     RenderWidgetHostView* view) {
-  if (RenderViewHostFactory::has_factory())
+  if (!view || RenderViewHostFactory::has_factory())
     return NULL;  // Can't cast to RenderWidgetHostViewAura in unit tests.
+  RenderProcessHostImpl* process = static_cast<RenderProcessHostImpl*>(
+      view->GetRenderWidgetHost()->GetProcess());
+  if (process->IsGuest())
+    return NULL;
   return static_cast<RenderWidgetHostViewAura*>(view);
 }