VM: Avoid allocating strings when disassembling code.

tests/language/disassemble_test.dart

 // Copyright (c) 2014, 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 isolate communication with
 // typed objects.
-// VMOptions=--disassemble
+// VMOptions=--disassemble --no-background-compilation
 // VMOptions=--disassemble --print-variable-descriptors --no-background-compilation
 
 // Tests proper object recognition in disassembler.
 
 f(x) {
  return "foo";
 }
 
 main() {
  print(f(0));
 }