Enable polymorphic inlining of StringBase [] and StringBase codeUnitAt

tests/language/vm/string_polymorphic_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.
+// Tests that the VM does not crash on weird corner cases of class Math.
+// VMOptions=--optimization_counter_threshold=10
+
+import 'package:expect/expect.dart';
+
+test1(String a, String b) {
+  return a == b;
+}
+
+var LEN = 500;
+
+var ITER = 10000000 / LEN;

[Florian Schneider, 2014/02/17 11:56:12]

The iteration count can probably be lower if you already use
optimization-counter-threshold=10.

[Cutch, 2014/02/18 17:00:30]

Done.

+
+measure(fn, a, b) {
+  for (var i = 0; i < ITER; i++) {
+    Expect.equals(true, fn(a, b));
+  }
+}  
+
+main() {
+  var n = LEN;
+  StringBuffer s = new StringBuffer();
+  for (var i=0; i < n; ++i) s.write("A");
+  String t = s.toString();
+  String u = s.toString();
+  String v = s.toString() + "\u1234";
+  String w = s.toString() + "\u1234";
+  for (var i=0; i<10; i++) measure(test1, t, u);
+  for (var i=0; i<10; i++) measure(test1, v, w);
+}