Change SDCHDictionaryFetcher to use URLRequest instead of URLFetcher.

net/url_request/url_fetcher_core.h

Index: net/url_request/url_fetcher_core.h
diff --git a/net/url_request/url_fetcher_core.h b/net/url_request/url_fetcher_core.h
index bddeaf4c88b88f4e3a96aa855c78ddd28bc6853b..584ce24fa26e10022b1e2371a0055f4b0273e2fb 100644
--- a/net/url_request/url_fetcher_core.h
+++ b/net/url_request/url_fetcher_core.h
@@ -251,13 +251,13 @@ class URLFetcherCore
   //
   // 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.