sync: Track validity of about:sync fields

sync/internal_api/public/sessions/sync_session_snapshot.cc

Index: sync/internal_api/public/sessions/sync_session_snapshot.cc
diff --git a/sync/internal_api/public/sessions/sync_session_snapshot.cc b/sync/internal_api/public/sessions/sync_session_snapshot.cc
index 4d966deef0371cf936bf30047971057f428240d2..42b990de03d7c70581dcd52647fef7a30ceb737c 100644
--- a/sync/internal_api/public/sessions/sync_session_snapshot.cc
+++ b/sync/internal_api/public/sessions/sync_session_snapshot.cc
@@ -21,7 +21,8 @@ SyncSessionSnapshot::SyncSessionSnapshot()
       num_server_conflicts_(0),
       notifications_enabled_(false),
       num_entries_(0),
-      retry_scheduled_(false) {
+      retry_scheduled_(false),
+      is_initialized_(false) {
 }
 
 SyncSessionSnapshot::SyncSessionSnapshot(
@@ -54,7 +55,8 @@ SyncSessionSnapshot::SyncSessionSnapshot(
       notifications_enabled_(notifications_enabled),
       num_entries_(num_entries),
       sync_start_time_(sync_start_time),
-      retry_scheduled_(retry_scheduled) {
+      retry_scheduled_(retry_scheduled),
+      is_initialized_(true) {
 }
 
 SyncSessionSnapshot::~SyncSessionSnapshot() {}
@@ -170,5 +172,9 @@ bool SyncSessionSnapshot::retry_scheduled() const {
   return retry_scheduled_;
 }
 
+bool SyncSessionSnapshot::is_initialized() const {
+  return is_initialized_;
+}
+
 }  // namespace sessions
 }  // namespace syncer