Add --no-background-compilation to tests that expect to run code in optimized form

tests/language/large_implicit_getter_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Dart test program for testing compilation of large implicit getters.
-// VMOptions=--optimization-counter-threshold=10
+// VMOptions=--optimization-counter-threshold=10 --no-background-compilation
 
 List<List> panels = [
 [6853.940039224797,6050.837897021371]
 ,[6953.240039224797,6050.837897021371]
 ,[7052.5400392247975,5885.237897021371]
 ,[7052.5400392247975,5719.637897021372]
 ,[7151.840039224798,5885.237897021371]
 ,[7052.5400392247975,6050.837897021371]
 ,[7052.5400392247975,6216.43789702137]
 ,[7052.5400392247975,6382.03789702137]
@@ skipping 1352 matching lines @@
 ,[2364.4759911280776,3842.7700224365044]
 ];
 
 
 main() {
   for (int i = 0; i < 20; i++) {
     var y = panels.length;
   }
 }