sync: Track validity of about:sync fields

chrome/browser/sync/profile_sync_service.h

Index: chrome/browser/sync/profile_sync_service.h
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index de9e00fa12e0b43b0b30b6072fd5c3d2d6db2df5..0bfb295f591ed0631a40311dc59f3dc38d003a72 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -288,7 +288,12 @@ class ProfileSyncService : public browser_sync::SyncFrontend,
 
   // Get various information for displaying in the user interface.
   std::string QuerySyncStatusSummary();
-  virtual browser_sync::SyncBackendHost::Status QueryDetailedSyncStatus();
+
+  // Initializes a struct of status indicators with data from the backend.
+  // Returns false if the backend was not available for querying; in that case
+  // the struct will be filled with default data.
+  virtual bool QueryDetailedSyncStatus(
+      browser_sync::SyncBackendHost::Status* result);
 
   virtual const GoogleServiceAuthError& GetAuthError() const;