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 9f86e6b5141fe09806ba98d806a93cff88f6991a..28c9cde65131d987a7b642ed2bca4c84085cf48b 100644
--- a/content/renderer/pepper/ppb_var_deprecated_impl.cc
+++ b/content/renderer/pepper/ppb_var_deprecated_impl.cc
@@ -290,7 +290,10 @@ 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) {