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

chrome/service/cloud_print/cloud_print_consts.cc

Index: chrome/service/cloud_print/cloud_print_consts.cc
===================================================================
--- chrome/service/cloud_print/cloud_print_consts.cc	(revision 67336)
+++ chrome/service/cloud_print/cloud_print_consts.cc	(working copy)
@@ -39,10 +39,6 @@
 // certain requests.
 const char kChromeCloudPrintProxyHeader[] = "X-Google-CloudPrint-Proxy: Chrome";
 
-// The request retry policy names. These strings are not valid hostnames, they
-// are just string keys.
-const char kCloudPrintAPIRetryPolicy[] = "cloudprint.google.com/api";
-const char kJobDataRetryPolicy[] = "cloudprint.google.com/jobdata";
 // The string to be appended to the user-agent for cloudprint requests.
 const char kCloudPrintUserAgent[] = "GoogleCloudPrintProxy";