Change SDCHDictionaryFetcher to use URLRequest instead of URLFetcher.

net/url_request/url_fetcher_core.h

 // 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.
 
 #ifndef NET_URL_REQUEST_URL_FETCHER_CORE_H_
 #define NET_URL_REQUEST_URL_FETCHER_CORE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 233 matching lines @@
   std::string upload_content_type_;  // MIME type of POST payload
   std::string referrer_;             // HTTP Referer header value and policy
   URLRequest::ReferrerPolicy referrer_policy_;
   bool is_chunked_upload_;           // True if using chunked transfer encoding
 
   // Used to determine how long to wait before making a request or doing a
   // retry.
   //
   // Both of them can only be accessed on the IO thread.
   //
-  // We need not only the throttler entry for |original_URL|, but also
-  // the one for |url|. For example, consider the case that URL A
-  // redirects to URL B, for which the server returns a 500
-  // response. In this case, the exponential back-off release time of
-  // URL A won't increase. If we retry without considering the
-  // back-off constraint of URL B, we may send out too many requests
-  // for URL A in a short period of time.
+  // To determine the proper backoff timing, throttler entries for
+  // both |original_URL| and |url| are needed. For example, consider
+  // the case that URL A redirects to URL B, for which the server
+  // returns a 500 response. In this case, the exponential back-off
+  // release time of URL A won't increase.  If only the backoff
+  // constraints for URL A are considered, too many requests for URL A
+  // may be sent in a short period of time.
   //
   // Both of these will be NULL if
   // URLRequestContext::throttler_manager() is NULL.
   scoped_refptr<URLRequestThrottlerEntryInterface>
       original_url_throttler_entry_;
   scoped_refptr<URLRequestThrottlerEntryInterface> url_throttler_entry_;
 
   // True if the URLFetcher has been cancelled.
   bool was_cancelled_;
 
@@ skipping 45 matching lines @@
   base::debug::StackTrace stack_trace_;
 
   static base::LazyInstance<Registry> g_registry;
 
   DISALLOW_COPY_AND_ASSIGN(URLFetcherCore);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_FETCHER_CORE_H_