Simulate transient error and verify exponential backoff.

chrome/browser/sync/sessions/session_state.cc

Index: chrome/browser/sync/sessions/session_state.cc
diff --git a/chrome/browser/sync/sessions/session_state.cc b/chrome/browser/sync/sessions/session_state.cc
index cb089d972cf887bf3a87e1a576ec19e44408e07c..5035ebd58a9f155565056ae0e87c550569f6d8c9 100644
--- a/chrome/browser/sync/sessions/session_state.cc
+++ b/chrome/browser/sync/sessions/session_state.cc
@@ -124,7 +124,8 @@ SyncSessionSnapshot::SyncSessionSnapshot(
     int num_conflicting_updates,
     bool did_commit_items,
     const SyncSourceInfo& source,
-    size_t num_entries)
+    size_t num_entries,
+    base::Time sync_start_time)
     : syncer_status(syncer_status),
       errors(errors),
       num_server_changes_remaining(num_server_changes_remaining),
@@ -138,7 +139,8 @@ SyncSessionSnapshot::SyncSessionSnapshot(
       num_conflicting_updates(num_conflicting_updates),
       did_commit_items(did_commit_items),
       source(source),
-      num_entries(num_entries){
+      num_entries(num_entries),
+      sync_start_time(sync_start_time) {
   for (int i = syncable::FIRST_REAL_MODEL_TYPE;
        i < syncable::MODEL_TYPE_COUNT; ++i) {
     const_cast<std::string&>(this->download_progress_markers[i]).assign(