Fix html/js test on Dartium.

Don't use identity check on strings, use equality instead.

R=kasperl@google.com
BUG=

Review URL: https://codereview.chromium.org//136953005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@32245 260f80e4-7a28-3924-810f-c04153c831b5

tests/html/js_test.dart

@@ -295,9 +295,9 @@ main() {
         // Test that we are not pulling cached proxy from the prototype
         // when asking for a proxy for the object.
         final proto = context['someProto'];
-        expect(proto['role'], same('proto'));
+        expect(proto['role'], equals('proto'));
         final obj = context['someObject'];
-        expect(obj['role'], same('object'));
+        expect(obj['role'], equals('object'));
       });
     });