Prevent crash on unrecoverable error method call on FrontendDataTypeControllers.

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 3aeed8398546381100d488b7acd11079551023af..20214e1409e0311f57a9c0ef55b09b1f8092dffe 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -103,7 +103,11 @@ struct UserShare;
 class ProfileSyncService : public browser_sync::SyncFrontend,
                            public browser_sync::SyncPrefObserver,
                            public browser_sync::UnrecoverableErrorHandler,
-                           public content::NotificationObserver {
+                           public content::NotificationObserver,
+                           // TODO(lipalani): crbug.com/100829. Instead of
+                           // doing this vend weak pointers from a factory.
+                           public base::SupportsWeakPtr<ProfileSyncService> {
+
  public:
   typedef ProfileSyncServiceObserver Observer;
   typedef browser_sync::SyncBackendHost::Status Status;