Implement exponential back-off mechanism and enforce it at the URLRequestHttpJob level.

net/url_request/url_request_throttler_header_adapter.cc

+// Copyright (c) 2010 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.
+
+#include "net/url_request/url_request_throttler_header_adapter.h"
+
+#include "net/http/http_response_headers.h"
+
+namespace net {
+
+URLRequestThrottlerHeaderAdapter::URLRequestThrottlerHeaderAdapter(
+    net::HttpResponseHeaders* headers)
+    : response_header_(headers) {
+}
+
+std::string URLRequestThrottlerHeaderAdapter::GetNormalizedValue(
+    const std::string& key) const {
+  std::string return_value;
+  response_header_->GetNormalizedHeader(key, &return_value);
+  return return_value;
+}
+
+int URLRequestThrottlerHeaderAdapter::GetResponseCode() const {
+  return response_header_->response_code();
+}
+
+}  // namespace net