Implement URLRequestBackoffManager for managing Backoff headers

net/url_request/url_request_context.h

Index: net/url_request/url_request_context.h
diff --git a/net/url_request/url_request_context.h b/net/url_request/url_request_context.h
index 54bded29140cc909b8622ff6fa88124c0c876cba..40581b085631b27fd06c786c09ed7e2f292f8355 100644
--- a/net/url_request/url_request_context.h
+++ b/net/url_request/url_request_context.h
@@ -41,6 +41,7 @@ class NetworkQualityEstimator;
 class SdchManager;
 class ProxyService;
 class URLRequest;
+class URLRequestBackoffManager;
 class URLRequestJobFactory;
 class URLRequestThrottlerManager;
 
@@ -183,6 +184,12 @@ class NET_EXPORT URLRequestContext
     throttler_manager_ = throttler_manager;
   }
 
+  // May be NULL.

[cpu_(ooo_6.6-7.5), 2015/07/17 19:56:01]

this comment should be the same style as 179 or 193

[xunjieli, 2015/07/20 20:02:13]

Done.

+  URLRequestBackoffManager* backoff_manager() const { return backoff_manager_; }
+  void set_backoff_manager(URLRequestBackoffManager* backoff_manager) {
+    backoff_manager_ = backoff_manager;
+  }
+
   // May return nullptr.
   SdchManager* sdch_manager() const { return sdch_manager_; }
   void set_sdch_manager(SdchManager* sdch_manager) {
@@ -245,6 +252,7 @@ class NET_EXPORT URLRequestContext
   HttpTransactionFactory* http_transaction_factory_;
   const URLRequestJobFactory* job_factory_;
   URLRequestThrottlerManager* throttler_manager_;
+  URLRequestBackoffManager* backoff_manager_;
   SdchManager* sdch_manager_;
   NetworkQualityEstimator* network_quality_estimator_;