Avoid entering an empty V8 context in PPB_Var_Deprecated IsInstanceOfDeprecated

content/renderer/pepper/ppb_var_deprecated_impl.cc

 // Copyright (c) 2012 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/renderer/pepper/ppb_var_deprecated_impl.h"
 
 #include <limits>
 
 #include "content/renderer/pepper/host_globals.h"
 #include "content/renderer/pepper/message_channel.h"
@@ skipping 272 matching lines @@
 }
 
 bool IsInstanceOfDeprecated(PP_Var var,
                             const PPP_Class_Deprecated* ppp_class,
                             void** ppp_class_data) {
   scoped_refptr<V8ObjectVar> object(V8ObjectVar::FromPPVar(var));
   if (!object.get())
     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) {
     if (ppp_class_data)
       *ppp_class_data = plugin_object->ppp_class_data();
     return true;
   }
 
   return false;
 }
@@ skipping 38 matching lines @@
       &CallDeprecated,
       &Construct,
       &IsInstanceOfDeprecated,
       &CreateObjectDeprecated,
       &CreateObjectWithModuleDeprecated, };
 
   return &var_deprecated_interface;
 }
 
 }  // namespace content