Handle birthday errors by disabling sync and deleting sync data.

chrome/browser/sync/sessions/sync_session.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A class representing an attempt to synchronize the local syncable data
 // store with a sync server. A SyncSession instance is passed as a stateful
 // bundle to and from various SyncerCommands with the goal of converging the
 // client view of data with that of the server. The commands twiddle with
 // session status in response to events and hiccups along the way, set and
 // query session progress with regards to conflict resolution and applying
@@ skipping 47 matching lines @@
     virtual bool IsSyncingCurrentlySilenced() = 0;
 
     // The client has been instructed to change its short poll interval.
     virtual void OnReceivedShortPollIntervalUpdate(
         const base::TimeDelta& new_interval) = 0;
 
     // The client has been instructed to change its long poll interval.
     virtual void OnReceivedLongPollIntervalUpdate(
         const base::TimeDelta& new_interval) = 0;
 
+    // The client needs to cease and desist syncing at once.  This occurs when
+    // 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).
+    virtual void OnShouldStopSyncingPermanently() = 0;
+
    protected:
     virtual ~Delegate() {}
   };
 
   // Creates a new SyncSession with mandatory context and delegate.
   SyncSession(SyncSessionContext* context, Delegate* delegate);
 
   // Builds a thread-safe and read-only copy of the current session state.
   SyncSessionSnapshot TakeSnapshot() const;
 
@@ skipping 74 matching lines @@
 
  private:
   SyncSession* session_;
   DISALLOW_COPY_AND_ASSIGN(ScopedSetSessionWriteTransaction);
 };
 
 }  // namespace sessions
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_SESSIONS_SYNC_SESSION_H_