Server directed error handling backend code.

chrome/browser/sync/sessions/sync_session.h

Index: chrome/browser/sync/sessions/sync_session.h
diff --git a/chrome/browser/sync/sessions/sync_session.h b/chrome/browser/sync/sessions/sync_session.h
index 9520f9dcfe65515245cde396d429a24049bb4eb4..8e73af7783a30db2ce0bad9f3e5e6c7619b0b903 100644
--- a/chrome/browser/sync/sessions/sync_session.h
+++ b/chrome/browser/sync/sessions/sync_session.h
@@ -79,8 +79,19 @@ class SyncSession {
     // the Syncer detects that the backend store has fundamentally changed or
     // is a different instance altogether (e.g. swapping from a test instance
     // to production, or a global stop syncing operation has wiped the store).
+    // TODO(lipalani) : Replace this function with the two below. This function
+    // stops the current sync cycle and purges the client. In the new model
+    // the former would be done by the |OnRequestEarlyExit| and
+    // the latter(which is an action) would be done in ProfileSyncService
+    // along with the rest of the actions.
     virtual void OnShouldStopSyncingPermanently() = 0;
 
+    // Stop the current sync cycle.
+    virtual void OnRequestEarlyExit() = 0;
+
+    // Notifies the front end that there is an actionable error.
+    virtual void OnActionableError(sessions::SyncSession* session) = 0;
+
    protected:
     virtual ~Delegate() {}
   };