Implement Strings API.

dart/frog/leg/lib/mockimpl.dart

 // 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.
 
 // Mocks of classes and interfaces that Leg cannot read directly.
 
 // TODO(ahe): Remove this file.
 
 class JSSyntaxRegExp implements RegExp {
   JSSyntaxRegExp(String pattern,
@@ skipping 14 matching lines @@
     throw 'factory ReceivePort is not implemented';
   }
 
   factory ReceivePort.singleShot() {
     throw 'factory ReceivePort.singleShot is not implemented';
   }
 }
 
 class StringBase {
   static String createFromCharCodes(List<int> charCodes) {
-    throw "StringBase.createFromCharCodes is not implemented";
+    checkNull(charCodes);
+    if (!isJSArray(charCodes)) {
+      charCodes = new List.from(charCodes);
+    }
+    return Primitives.stringFromCharCodes(charCodes);
   }
 
   static String join(List<String> strings, String separator) {
-    throw "StringBase.join is not implemented";
+    checkNull(strings);
+    checkNull(separator);
+    if (separator is !String) throw new IllegalArgumentException(separator);
+    var result = "";
+    var first = true;
+    for (var string in strings) {
+      checkNull(string);
+      if (string is !String) throw new IllegalArgumentException(string);
+      if (!first) result += separator; // TODO(ahe): Use string buffer.
+      result += string; // TODO(ahe): Use string buffer.
+      first = false;
+    }
+    return result;
   }
 
   static String concatAll(List<String> strings) {
-    throw "StringBase.concatAll is not implemented";
+    checkNull(strings);
+    var result = "";
+    for (var string in strings) {
+      checkNull(string);
+      if (string is !String) throw new IllegalArgumentException(string);
+      result += string; // TODO(ahe): Use string buffer.
+    }
+    return result;
   }
 }
 
 class TimeZoneImplementation implements TimeZone {
   const TimeZoneImplementation.utc() : isUtc = true;
   TimeZoneImplementation.local() : isUtc = false;
 
   bool operator ==(Object other) {
     if (!(other is TimeZoneImplementation)) return false;
     return isUtc == other.isUtc;
@@ skipping 377 matching lines @@
   factory List([int length]) => Primitives.newList(length);
   factory List.from(Iterable<E> other) {
     List<E> result = new List<E>();
     Iterator<E> iterator = other.iterator();
     while (iterator.hasNext()) {
       result.add(iterator.next());
     }
     return result;
   }
 }