[Android] Use resource throttle instead of HandleExternalProtocol.

android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.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 "android_webview/browser/renderer_host/aw_resource_dispatcher_host_delegate.h"
 
 #include "android_webview/browser/aw_login_delegate.h"
 #include "android_webview/browser/aw_contents_io_thread_client.h"
 #include "android_webview/common/url_constants.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 97 matching lines @@
   return true;
 }
 
 content::ResourceDispatcherHostLoginDelegate*
     AwResourceDispatcherHostDelegate::CreateLoginDelegate(
         net::AuthChallengeInfo* auth_info,
         net::URLRequest* request) {
   return new AwLoginDelegate(auth_info, request);
 }
 
-void AwResourceDispatcherHostDelegate::HandleExternalProtocol(const GURL& url,
+bool AwResourceDispatcherHostDelegate::HandleExternalProtocol(const GURL& url,
                                                               int child_id,
                                                               int route_id) {
   // The AwURLRequestJobFactory implementation should ensure this method never
   // gets called.
   NOTREACHED();
+  return false;
 }
 
 void AwResourceDispatcherHostDelegate::SetOnlyAllowLoadFromCache(
     net::URLRequest* request) {
   int load_flags = request->load_flags();
   load_flags &= ~(net::LOAD_BYPASS_CACHE &
                   net::LOAD_VALIDATE_CACHE &
                   net::LOAD_PREFERRING_CACHE);
   load_flags |= net::LOAD_ONLY_FROM_CACHE;
   request->set_load_flags(load_flags);
 }
 
 }