Remove implementations of mirror methods not in the API from the VM. Update tests.

pkg/unittest/lib/mirror_matchers.dart

Index: pkg/unittest/lib/mirror_matchers.dart
diff --git a/pkg/unittest/lib/mirror_matchers.dart b/pkg/unittest/lib/mirror_matchers.dart
index 7d1597f2ac27f59c752109141a93a6a58ce6c51c..93656807269d3a82093826b4c84fa4af2c7f29e9 100644
--- a/pkg/unittest/lib/mirror_matchers.dart
+++ b/pkg/unittest/lib/mirror_matchers.dart
@@ -49,7 +49,13 @@ class _HasProperty extends Matcher {
     var mirror = reflect(item);
     var classMirror = mirror.type;
     var symbol = new Symbol(_name);
-    if (!classMirror.getters.containsKey(symbol)) {
+    bool hasGetter(classMirror, getterName) {
+      var candidate = classMirror.declarations[getterName];
+      return candidate != null &&
+          candidate is MethodMirror &&
+          candidate.isGetter;
+    }
+    if (!hasGetter(classMirror, symbol)) {
       addStateInfo(matchState, {'reason': 'has no property named "$_name"'});
       return false;
     }