diff --git a/frontend_server/lib/server.dart b/frontend_server/lib/server.dart
index 804c5699e..572087e9d 100644
--- a/frontend_server/lib/server.dart
+++ b/frontend_server/lib/server.dart
@@ -39,6 +39,11 @@ class _FlutterFrontendCompiler implements frontend.CompilerInterface{
     _compiler.acceptLastDelta();
   }
 
+  @override
+  Future<Null> rejectLastDelta() async {
+    return _compiler.rejectLastDelta();
+  }
+
   @override
   void invalidate(Uri uri) {
     _compiler.invalidate(uri);

Patch engine until next dart roll lands
[hhh] Patch engine until next dart roll lands

Incompatible change landed https://dart-review.googlesource.com/c/sdk/+/72540.

Change-Id: I618650964ec953ae8f0efe9c45e59ecd356a2840
Reviewed-on: https://dart-review.googlesource.com/73685
Reviewed-by: Martin Kustermann <a35dd5b79fac84b2bb3b026a16b8becc55af5961@google.com>
Reviewed-by: Ben Konyi <67ffcaedcc3dc3d87dddb9627b72dd41756b31b1@google.com>
