Make reftests work for sky.

sky/tests/harness/reftest-mismatch.sky

Index: sky/tests/harness/reftest-mismatch.sky
diff --git a/sky/tests/harness/reftest-mismatch.sky b/sky/tests/harness/reftest-mismatch.sky
new file mode 100644
index 0000000000000000000000000000000000000000..c5fe9e3d31c1abce1a49afb64d245872fc482121
--- /dev/null
+++ b/sky/tests/harness/reftest-mismatch.sky
@@ -0,0 +1,13 @@
+<foo>
+This is a mismatch reftest. Should not match.
+<script>
+window.addEventListener('load', function() {
+    // TODO(ojan): Why is this setTimeout needed to get
+    // a non-white page. It seems we don't do our first
+    // paint before the load event?
+    setTimeout(function() {
+        internals.notifyTestComplete("");
+    });
+})
+</script>
+</foo>