Fix issue 11214 avoid length overflow in String::ConcatAll

tests/language/string_overflow.dart

Index: tests/language/string_overflow.dart
===================================================================
--- tests/language/string_overflow.dart	(revision 0)
+++ tests/language/string_overflow.dart	(revision 0)
@@ -0,0 +1,24 @@
+// 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.
+
+// Test to ensure that the VM does not have an integer overflow issue
+// when concatenating strings.
+
+import "package:expect/expect.dart";
+
+main()
+{
+  String a = "a";
+  for( ; a.length < 256 * 1024 * 1024 ; )
+    a = a + a;
+
+  var exception_thrown = false;
+  try {
+    var concat = "$a$a$a$a$a$a$a$a";
+  } on OutOfMemoryError catch (exc) {
+    exception_thrown = true;
+  }
+  Expect.isTrue(exception_thrown);
+}
+