Add support for Expect.equals in the Leg core library.

frog/leg/lib/core.dart

 // Copyright (c) 2011, 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.
 
 void print(var obj) {
   // TODO(ngeoffray): enable when the parser accepts it.
   // obj = obj.toString();
   var hasConsole = JS(@"typeof console == 'object'");
   if (hasConsole) {
     JS(@"console.log($0)", obj);
@@ skipping 231 matching lines @@
   throw "Unimplemented user-defined length.";
 }
 
 class int {}
 class double {}
 class String {}
 class bool {}
 class Object {}
 class List<T> {}
 
+class Expect {
+  static void equals(var expected, var actual) {
+    if (expected == actual) return;
+    print('Expect.equals(expected: <' + expected.toString() +
+          '>, actual:<' + actual.toString() + '> fails.');
+    throw 'Expect.equals failed.';
+  }
+}
+
 class Stopwatch {
   double startMs;
   double elapsedMs;
 
   Stopwatch() {
     elapsedMs = 0.0;
   }
 
   void start() {
     if (startMs == null) {
@@ skipping 26 matching lines @@
       return JS(@"Math.floor($0)", elapsedMs);
     } else {
       return JS(@"Math.floor($0 + (Date.now() - $1))", elapsedMs, startMs);
     }
   }
 
   int frequency() {
     return 1000;
   }
 }