Enable the Fetch API for extensions which service workers are supported.

extensions/renderer/dispatcher.cc

 // Copyright 2014 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 "extensions/renderer/dispatcher.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/containers/scoped_ptr_map.h"
@@ skipping 1549 matching lines @@
   // The "guestViewDeny" module must always be loaded last. It registers
   // error-providing custom elements for the GuestView types that are not
   // available, and thus all of those types must have been checked and loaded
   // (or not loaded) beforehand.
   if (context_type == Feature::BLESSED_EXTENSION_CONTEXT) {
     module_system->Require("guestViewDeny");
   }
 }
 
 void Dispatcher::AddChannelSpecificFeatures() {
-  // chrome-extension: resources should be allowed to register a Service Worker.
   if (FeatureProvider::GetBehaviorFeature(BehaviorFeature::kServiceWorker)
           ->IsAvailableToEnvironment()
-          .is_available())
-    WebSecurityPolicy::registerURLSchemeAsAllowingServiceWorkers(
-        WebString::fromUTF8(kExtensionScheme));
+          .is_available()) {
+    // If chrome-extension: is allowed to register service workers, register it
+    // as an allowed scheme for both service workers and the Fetch API.
+    WebString scheme = WebString::fromUTF8(kExtensionScheme);
+    WebSecurityPolicy::registerURLSchemeAsAllowingServiceWorkers(scheme);
+    WebSecurityPolicy::registerURLSchemeAsSupportingFetchAPI(scheme);
+  }
 }
 
 }  // namespace extensions