Ensure variable holder is a fast-mode object

Change-Id: I660e987f319bd4b23b9347a8c819635ceaddae68
Reviewed-on: https://dart-review.googlesource.com/c/87611
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

@@ -451,6 +451,7 @@ var #staticStateDeclaration = {};
 
 // Ensure holders are in fast mode, now we have finished adding things.
 convertAllToFastObject(holders);
+convertToFastObject(#staticState);
 
 // Invokes main (making sure that it records the 'current-script' value).
 #invokeMain;