Introduce a delegate to avoid hardcoding "chrome-extension" in net/.

net/base/network_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 "net/base/network_delegate.h"
 
 #include "base/logging.h"
 #include "net/base/load_flags.h"
 #include "net/url_request/url_request.h"
 
@@ skipping 95 matching lines @@
   DCHECK(!(request.load_flags() & net::LOAD_DO_NOT_SAVE_COOKIES));
   return OnCanSetCookie(request, cookie_line, options);
 }
 
 bool NetworkDelegate::CanAccessFile(const URLRequest& request,
                                     const FilePath& path) const {
   DCHECK(CalledOnValidThread());
   return OnCanAccessFile(request, path);
 }
 
+bool NetworkDelegate::CanThrottleRequest(const URLRequest& request) const {
+  DCHECK(CalledOnValidThread());
+  return OnCanThrottleRequest(request);
+}
+
 }  // namespace net