sync: raise initial backoff interval from 1 second to 5 minutes.

sync/internal_api/public/engine/polling_constants.cc

Index: sync/internal_api/public/engine/polling_constants.cc
diff --git a/sync/internal_api/public/engine/polling_constants.cc b/sync/internal_api/public/engine/polling_constants.cc
index d65994bdc7b62720b56295d65b4915b2dd3ca65e..38ef4f3c6d6b1c81aa46cac6201309a3127f89d9 100644
--- a/sync/internal_api/public/engine/polling_constants.cc
+++ b/sync/internal_api/public/engine/polling_constants.cc
@@ -22,5 +22,13 @@ const int64 kMaxBackoffSeconds = 60 * 60 * 4;  // 4 hours.
 // Backoff interval randomization factor.
 const int kBackoffRandomizationFactor = 2;
 
-}  // namespace syncer
+// After a failure contacting sync servers, specifies how long to wait before
+// reattempting and entering exponential backoff if consecutive failures
+// occur.
+const int kInitialBackoffRetrySeconds = 60 * 5;  // 5 minutes.
+
+// Similar to kInitialBackoffRetrySeconds above, but only to be used in
+// certain exceptional error cases, such as MIGRATION_DONE.
+const int kInitialBackoffShortRetrySeconds = 1;
 
+}  // namespace syncer