Revert "Revert "First iteration on custom layout.""

sky/engine/core/layout/LayoutCallback.h

Index: sky/engine/core/layout/LayoutCallback.h
diff --git a/sky/engine/core/layout/LayoutCallback.h b/sky/engine/core/layout/LayoutCallback.h
new file mode 100644
index 0000000000000000000000000000000000000000..0013f92194d584a1b9b00c6ea637214a9441236c
--- /dev/null
+++ b/sky/engine/core/layout/LayoutCallback.h
@@ -0,0 +1,18 @@
+// Copyright 2015 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.
+
+#ifndef SKY_ENGINE_CORE_PAINTING_LAYOUTCALLBACK_H_
+#define SKY_ENGINE_CORE_PAINTING_LAYOUTCALLBACK_H_
+
+namespace blink {
+
+class LayoutCallback {
+public:
+    virtual ~LayoutCallback() {}
+    virtual void handleEvent() = 0;
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_LAYOUTCALLBACK_H_