Initial version of mocking support. There is still quite a bit of

tests/lib/unittest/test_utils.dart

Index: tests/lib/unittest/test_utils.dart
===================================================================
--- tests/lib/unittest/test_utils.dart	(revision 9180)
+++ tests/lib/unittest/test_utils.dart	(working copy)
@@ -20,11 +20,11 @@
 }
 
 void shouldFail(value, Matcher matcher, expected) {
-  configureExpectHandler(_testHandler);
+  configureExpectFailureHandler(_testHandler);
   errorCount = 0;
   errorString = '';
   expect(value, matcher);
-  configureExpectHandler(null);
+  configureExpectFailureHandler(null);
   expect(errorCount, equals(1));
   if (expected is String) {
     expect(errorString, equalsIgnoringWhitespace(expected));
@@ -34,11 +34,11 @@
 }
 
 void shouldPass(value, Matcher matcher) {
-  configureExpectHandler(_testHandler);
+  configureExpectFailureHandler(_testHandler);
   errorCount = 0;
   errorString = '';
   expect(value, matcher);
-  configureExpectHandler(null);
+  configureExpectFailureHandler(null);
   expect(errorCount, equals(0));
 }