Avoid entering an empty V8 context in PPB_Var_Deprecated IsInstanceOfDeprecated

content/renderer/pepper/ppb_var_deprecated_impl.cc

Index: content/renderer/pepper/ppb_var_deprecated_impl.cc
diff --git a/content/renderer/pepper/ppb_var_deprecated_impl.cc b/content/renderer/pepper/ppb_var_deprecated_impl.cc
index def6a8d50069d7fecf783f86a97067f7d32b795d..c5a93e2f38960f4590c24a726b5bfe96625ebec2 100644
--- a/content/renderer/pepper/ppb_var_deprecated_impl.cc
+++ b/content/renderer/pepper/ppb_var_deprecated_impl.cc
@@ -303,7 +303,10 @@ bool IsInstanceOfDeprecated(PP_Var var,
     return false;  // Not an object at all.
 
   v8::HandleScope handle_scope(object->instance()->GetIsolate());
-  v8::Context::Scope context_scope(object->instance()->GetMainWorldContext());
+  v8::Handle<v8::Context> context = object->instance()->GetMainWorldContext();
+  if (context.IsEmpty())
+    return false;
+  v8::Context::Scope context_scope(context);
   PluginObject* plugin_object = PluginObject::FromV8Object(
       object->instance()->GetIsolate(), object->GetHandle());
   if (plugin_object && plugin_object->ppp_class() == ppp_class) {