Make reftests work for sky.

sky/compositor/display_delegate.cc

Index: sky/compositor/display_delegate.cc
diff --git a/sky/compositor/display_delegate.cc b/sky/compositor/display_delegate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c868558424aca3e1a5305ee3515ce542bc3d8d98
--- /dev/null
+++ b/sky/compositor/display_delegate.cc
@@ -0,0 +1,24 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sky/compositor/display_delegate.h"
+
+namespace sky {
+
+static CreateDisplayDelegate createDisplayDelegateFunction = 0;
+
+void DisplayDelegate::setDisplayDelegateCreateFunction(CreateDisplayDelegate createFunction)
+{
+    DCHECK(createFunction);
+    DCHECK(!createDisplayDelegateFunction);
+    createDisplayDelegateFunction = createFunction;
+}
+
+DisplayDelegate* DisplayDelegate::create(LayerClient* client)
+{
+    DCHECK(createDisplayDelegateFunction);
+    return createDisplayDelegateFunction(client);
+}
+
+}  // namespace sky