Lazily load extension API schemas

chrome/common/extensions/features/permission_feature.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/common/extensions/features/permission_feature.h"
 
 namespace extensions {
 
 PermissionFeature::PermissionFeature() {
 }
 
 PermissionFeature::~PermissionFeature() {
 }
 
 Feature::Availability PermissionFeature::IsAvailableToContext(
     const Extension* extension,
     Feature::Context context,
+    const GURL& url,
     Feature::Platform platform) const {
   Availability availability = SimpleFeature::IsAvailableToContext(extension,
                                                                   context,
+                                                                  url,
                                                                   platform);
   if (!availability.is_available())
     return availability;
 
-  if (!extension->HasAPIPermission(name()))
+  if (extension && !extension->HasAPIPermission(name()))
     return CreateAvailability(NOT_PRESENT, extension->GetType());
 
   return CreateAvailability(IS_AVAILABLE);
 }
 
 }  // namespace