Add IsEmpty() check to blind IsUndefined() check in ExtensionDispatcher.

chrome/renderer/extensions/extension_dispatcher.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 "chrome/renderer/extensions/extension_dispatcher.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_piece.h"
@@ skipping 676 matching lines @@
   module_system->RegisterNativeHandler("lazy_background_page",
       scoped_ptr<NativeHandler>(new LazyBackgroundPageNativeHandler(this)));
   module_system->RegisterNativeHandler("channel",
       scoped_ptr<NativeHandler>(new ChannelNativeHandler(
           static_cast<chrome::VersionInfo::Channel>(chrome_channel_))));
   // Create the 'chrome' variable if it doesn't already exist.
   {
     v8::HandleScope handle_scope;
     v8::Handle<v8::String> chrome_string(v8::String::New("chrome"));
     v8::Handle<v8::Object> global(v8::Context::GetCurrent()->Global());
-    if (global->Get(chrome_string)->IsUndefined())
+    v8::Handle<v8::Value> chrome(global->Get(chrome_string));
+    if (chrome.IsEmpty() || chrome->IsUndefined())
       global->Set(chrome_string, v8::Object::New());
   }
 
   // Loading JavaScript is expensive, so only run the full API bindings
   // generation mechanisms in extension pages (NOT all web pages).
   switch (context_type) {
     case Feature::UNSPECIFIED_CONTEXT:
     case Feature::WEB_PAGE_CONTEXT:
       // TODO(kalman): see comment below about ExtensionAPI.
       InstallBindings(module_system.get(), v8_context, "app");
@@ skipping 322 matching lines @@
   // APIs, they don't get extension bindings injected. If we end up here it
   // means that a sandboxed page somehow managed to invoke an API anyway, so
   // we should abort.
   WebKit::WebFrame* frame = context->web_frame();
   ExtensionURLInfo url_info(frame->document().securityOrigin(),
       UserScriptSlave::GetDataSourceURLForFrame(frame));
   CHECK(!extensions_.IsSandboxedPage(url_info));
 
   return true;
 }