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..a50225c6cb7c8579c08a64efed37c0ae42ae2c82 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;
 
@@ -184,6 +185,12 @@ class NET_EXPORT URLRequestContext
   }
 
   // May return nullptr.
+  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) {
     sdch_manager_ = 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_;