Simulate transient error and verify exponential backoff.

chrome/browser/sync/sessions/status_controller.h

Index: chrome/browser/sync/sessions/status_controller.h
diff --git a/chrome/browser/sync/sessions/status_controller.h b/chrome/browser/sync/sessions/status_controller.h
index f8c6893dc1804e64b98277d96c75a1f1eedcb10d..3dfb6e08ab19af001816676ca7060981fd0e16f4 100644
--- a/chrome/browser/sync/sessions/status_controller.h
+++ b/chrome/browser/sync/sessions/status_controller.h
@@ -37,6 +37,7 @@
 #include <map>
 
 #include "base/stl_util.h"
+#include "base/time.h"
 #include "chrome/browser/sync/sessions/ordered_commit_set.h"
 #include "chrome/browser/sync/sessions/session_state.h"
 
@@ -192,6 +193,11 @@ class StatusController {
     return group_restriction_;
   }
 
+  base::Time sync_start_time() const {
+    // The time at which we sent the first GetUpdates command for this sync.
+    return sync_start_time_;
+  }
+
   // Check whether a particular model is included by the active group
   // restriction.
   bool ActiveGroupRestrictionIncludesModel(syncable::ModelType model) const {
@@ -259,6 +265,8 @@ class StatusController {
 
   const ModelSafeRoutingInfo routing_info_;
 
+  base::Time sync_start_time_;
+
   DISALLOW_COPY_AND_ASSIGN(StatusController);
 };