Implement exponential back-off mechanism.

net/url_request/url_request_throttler_header_adapter.h

Index: net/url_request/url_request_throttler_header_adapter.h
diff --git a/net/url_request/url_request_throttler_header_adapter.h b/net/url_request/url_request_throttler_header_adapter.h
new file mode 100644
index 0000000000000000000000000000000000000000..599a9f6598d26b19988a16708ba82cfd47da4424
--- /dev/null
+++ b/net/url_request/url_request_throttler_header_adapter.h
@@ -0,0 +1,34 @@
+// 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.
+
+#ifndef NET_URL_REQUEST_URL_REQUEST_THROTTLER_HEADER_ADAPTER_H_
+#define NET_URL_REQUEST_URL_REQUEST_THROTTLER_HEADER_ADAPTER_H_
+
+#include <string>
+
+#include "base/ref_counted.h"
+#include "net/url_request/url_request_throttler_header_interface.h"
+
+namespace net {
+
+class HttpResponseHeaders;
+
+// Adapter for the HTTP header interface of the URL request throttler component.
+class URLRequestThrottlerHeaderAdapter
+    : public URLRequestThrottlerHeaderInterface {
+ public:
+  explicit URLRequestThrottlerHeaderAdapter(net::HttpResponseHeaders* headers);
+  virtual ~URLRequestThrottlerHeaderAdapter() {}
+
+  // Implementation of URLRequestThrottlerHeaderInterface
+  virtual std::string GetNormalizedValue(const std::string& key) const;
+  virtual int GetResponseCode() const;
+
+ private:
+  const scoped_refptr<net::HttpResponseHeaders> response_header_;
+};
+
+}  // namespace net
+
+#endif  // NET_URL_REQUEST_URL_REQUEST_THROTTLER_HEADER_ADAPTER_H_