Implement URLRequestBackoffManager for managing Backoff headers

net/url_request/url_request_context_storage.cc

Index: net/url_request/url_request_context_storage.cc
diff --git a/net/url_request/url_request_context_storage.cc b/net/url_request/url_request_context_storage.cc
index 2851935871944b2e97a98c00ed98fbf67cfd174c..e1452be9b351d78f9f50ccfd29c13e261a6c5d4e 100644
--- a/net/url_request/url_request_context_storage.cc
+++ b/net/url_request/url_request_context_storage.cc
@@ -19,6 +19,7 @@
 #include "net/ssl/channel_id_service.h"
 #include "net/url_request/fraudulent_certificate_reporter.h"
 #include "net/url_request/http_user_agent_settings.h"
+#include "net/url_request/url_request_backoff_manager.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_job_factory.h"
 #include "net/url_request/url_request_throttler_manager.h"
@@ -119,6 +120,12 @@ void URLRequestContextStorage::set_throttler_manager(
   throttler_manager_.reset(throttler_manager);
 }
 
+void URLRequestContextStorage::set_backoff_manager(
+    URLRequestBackoffManager* backoff_manager) {
+  context_->set_backoff_manager(backoff_manager);
+  backoff_manager_.reset(backoff_manager);
+}
+
 void URLRequestContextStorage::set_http_user_agent_settings(
     HttpUserAgentSettings* http_user_agent_settings) {
   context_->set_http_user_agent_settings(http_user_agent_settings);