Record size of scroller that user scrolls

third_party/WebKit/Source/platform/scroll/ScrollerSize.h

Index: third_party/WebKit/Source/platform/scroll/ScrollerSize.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollerSize.h b/third_party/WebKit/Source/platform/scroll/ScrollerSize.h
new file mode 100644
index 0000000000000000000000000000000000000000..a2ddc090ee29bedf33a0e490686098a1d3fa48d2
--- /dev/null
+++ b/third_party/WebKit/Source/platform/scroll/ScrollerSize.h
@@ -0,0 +1,14 @@
+// Copyright 2017 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 ScrollerSize_h
+#define ScrollerSize_h
+
+#include "cc/trees/layer_tree_host_impl.h"
+
+namespace blink {
+using cc::LayerTreeHostImpl;
+}
+
+#endif  // ScrollerSize_h