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

net/request_throttler/request_throttler_entry_interface.h

+// 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_REQUEST_THROTTLER_REQUEST_THROTTLER_ENTRY_INTERFACE_H_
+#define NET_REQUEST_THROTTLER_REQUEST_THROTTLER_ENTRY_INTERFACE_H_
+
+#include "base/ref_counted.h"
+#include "base/time.h"
+
+class RequestThrottlerHeaderInterface;
+
+// Represents an entry of the request throttler manager.
+class RequestThrottlerEntryInterface
+    : public base::RefCountedThreadSafe<RequestThrottlerEntryInterface> {
+ public:
+  RequestThrottlerEntryInterface() {}
+
+  // This method needs to be called prior to every request; if it returns
+  // false, the calling module must cancel its current request.
+  virtual bool IsRequestAllowed() const = 0;
+
+  // This method needs to be called each time a response is received.
+  virtual void UpdateWithResponse(
+      const RequestThrottlerHeaderInterface* response) = 0;
+
+  // This method needs to be called each time when a request is actually sent.
+  virtual void NotifyRequestStart() = 0;
+
+ protected:
+  virtual ~RequestThrottlerEntryInterface() {}
+ private:
+  friend class base::RefCountedThreadSafe<RequestThrottlerEntryInterface>;
+  DISALLOW_COPY_AND_ASSIGN(RequestThrottlerEntryInterface);
+};
+
+#endif  // NET_REQUEST_THROTTLER_REQUEST_THROTTLER_ENTRY_INTERFACE_H_