Handle birthday errors by disabling sync and deleting sync data.

chrome/browser/sync/engine/syncapi.h

 // Copyright (c) 2010 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.
 
 // This file defines the "sync API", an interface to the syncer
 // backend that exposes (1) the core functionality of maintaining a consistent
 // local snapshot of a hierarchical object set; (2) a means to transactionally
 // access and modify those objects; (3) a means to control client/server
 // synchronization tasks, namely: pushing local object modifications to a
 // server, pulling nonlocal object modifications from a server to this client,
@@ skipping 644 matching lines @@
     // WARNING: Calling methods on the SyncManager before receiving this
     // message, unless otherwise specified, produces undefined behavior.
     virtual void OnInitializationComplete() = 0;
 
     // The syncer thread has been paused.
     virtual void OnPaused() = 0;
 
     // The syncer thread has been resumed.
     virtual void OnResumed() = 0;
 
+    // We are no longer permitted to communicate with the server. Sync should
+    // be disabled and state cleaned up at once.  This can happen for a number
+    // of reasons, e.g. swapping from a test instance to production, or a
+    // global stop syncing operation has wiped the store.
+    virtual void OnStopSyncingPermanently() = 0;
+
    private:
     DISALLOW_COPY_AND_ASSIGN(Observer);
   };
 
   // Create an uninitialized SyncManager.  Callers must Init() before using.
   SyncManager();
   virtual ~SyncManager();
 
   // Initialize the sync manager.  |database_location| specifies the path of
   // the directory in which to locate a sqlite repository storing the syncer
@@ skipping 199 matching lines @@
   // This allows actual HttpPostProvider subclass implementations to be
   // reference counted, which is useful if a particular implementation uses
   // multiple threads to serve network requests.
   virtual void Destroy(HttpPostProviderInterface* http) = 0;
   virtual ~HttpPostProviderFactory() { }
 };
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCAPI_H_