Unify String.

runtime/lib/string_patch.dart

Index: runtime/lib/string_patch.dart
diff --git a/runtime/lib/string_patch.dart b/runtime/lib/string_patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..07f3818027962bca0c14cbef3775c71a07cb7a1c
--- /dev/null
+++ b/runtime/lib/string_patch.dart
@@ -0,0 +1,17 @@
+// Copyright (c) 2012, 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.
+
+patch class StringImplementation {
+  /* patch */ static String _fromCharCodes(List<int> charCodes) {
+    return StringBase.createFromCharCodes(charCodes);
+  }
+
+  /* patch */ static String join(List<String> strings, String separator) {
+    return StringBase.join(strings, separator);
+  }
+
+  /* patch */ static String concatAll(List<String> strings) {
+    return StringBase.concatAll(strings);
+  }
+}