Port and integrate the irregexp engine from V8

tests/language/regex/results-cache_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.
+
+import 'util.dart';
+import 'package:expect/expect.dart';
+
+void main() {
+  // Long string to trigger caching.
+  var string =
+  """Friends, Romans, countrymen, lend me your ears!
+  I come to bury Caesar, not to praise him.
+  The evil that men do lives after them,
+  The good is oft interred with their bones;
+  So let it be with Caesar. The noble Brutus
+  Hath told you Caesar was ambitious;
+  If it were so, it was a grievous fault,
+  And grievously hath Caesar answer'd it.
+  Here, under leave of Brutus and the rest-
+  For Brutus is an honorable man;
+  So are they all, all honorable men-
+  Come I to speak in Caesar's funeral.
+  He was my friend, faithful and just to me;
+  But Brutus says he was ambitious,
+  And Brutus is an honorable man.
+  He hath brought many captives home to Rome,
+  Whose ransoms did the general coffers fill.
+  Did this in Caesar seem ambitious?
+  When that the poor have cried, Caesar hath wept;
+  Ambition should be made of sterner stuff:
+  Yet Brutus says he was ambitious,
+  And Brutus is an honorable man.
+  You all did see that on the Lupercal
+  I thrice presented him a kingly crown,
+  Which he did thrice refuse. Was this ambition?
+  Yet Brutus says he was ambitious,
+  And sure he is an honorable man.
+  I speak not to disprove what Brutus spoke,
+  But here I am to speak what I do know.
+  You all did love him once, not without cause;
+  What cause withholds you then to mourn for him?
+  O judgement, thou art fled to brutish beasts,
+  And men have lost their reason. Bear with me;
+  My heart is in the coffin there with Caesar,
+  And I must pause till it come back to me.""";
+
+  var replaced = string.replaceAll(new RegExp(r"\b\w+\b"), "foo");
+  for (var i = 0; i < 3; i++) {
+    assertEquals(replaced,
+                string.replaceAll(new RegExp(r"\b\w+\b"), "foo"));
+  }
+
+  // Check that the result is in a COW array.
+  var words = string.split(" ");
+  assertEquals("Friends,", words[0]);
+  words[0] = "Enemies,";
+  words = string.split(" ");
+  assertEquals("Friends,", words[0]);
+}