Make hit testing work in layout2.dart

sky/engine/core/view/BeginFrameCallback.h

Index: sky/engine/core/view/BeginFrameCallback.h
diff --git a/sky/engine/core/view/BeginFrameCallback.h b/sky/engine/core/view/BeginFrameCallback.h
new file mode 100644
index 0000000000000000000000000000000000000000..8b1faee1241b22f768bd603e4a5d101283f75a32
--- /dev/null
+++ b/sky/engine/core/view/BeginFrameCallback.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_VIEW_BEGINFRAMECALLBACK_H_
+#define SKY_ENGINE_CORE_VIEW_BEGINFRAMECALLBACK_H_
+
+namespace blink {
+
+class BeginFrameCallback {
+public:
+    virtual ~BeginFrameCallback() { }
+    virtual bool handleEvent(double highResTime) = 0;
+};
+
+}
+
+#endif  // SKY_ENGINE_CORE_VIEW_BEGINFRAMECALLBACK_H_