Introduce the plumbing necessary to report Unrecoverable error from model safe workers.

chrome/browser/sync/internal_api/sync_manager.h

Index: chrome/browser/sync/internal_api/sync_manager.h
diff --git a/chrome/browser/sync/internal_api/sync_manager.h b/chrome/browser/sync/internal_api/sync_manager.h
index 650893d2aba22d7f89deeae55187d8fcfc10fdc7..94062772a8e386ff0dafb0756983241b897f78e2 100644
--- a/chrome/browser/sync/internal_api/sync_manager.h
+++ b/chrome/browser/sync/internal_api/sync_manager.h
@@ -383,6 +383,11 @@ class SyncManager {
     virtual void OnActionableError(
         const browser_sync::SyncProtocolError& sync_protocol_error) = 0;
 
+    // Called by the syncer when it encouters an unrecoverable error.
+    virtual void OnUnrecoverableError(
+        const tracked_objects::Location& location,
+        const std::string& message) = 0;
+
    protected:
     virtual ~Observer();
   };