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

chrome/common/net/url_fetcher.h

Index: chrome/common/net/url_fetcher.h
===================================================================
--- chrome/common/net/url_fetcher.h	(revision 64189)
+++ chrome/common/net/url_fetcher.h	(working copy)
@@ -152,6 +152,10 @@
   // after backoff_delay() elapses. URLFetcher has it set to true by default.
   void set_automatically_retry_on_5xx(bool retry);
 
+  int max_retries() const { return max_retries_; }
+
+  void set_max_retries(int max_retries) { max_retries_ = max_retries; }
+
   // Returns the back-off delay before the request will be retried,
   // when a 5xx response was received.
   base::TimeDelta backoff_delay() const { return backoff_delay_; }
@@ -203,6 +207,8 @@
   bool automatically_retry_on_5xx_;
   // Back-off time delay. 0 by default.
   base::TimeDelta backoff_delay_;
+  // Maximum retris allowed.
+  int max_retries_;
 
   static bool g_interception_enabled;