Record size of scroller that user scrolls

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

Index: third_party/WebKit/Source/platform/scroll/ScrollerSizeMetrics.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollerSizeMetrics.h b/third_party/WebKit/Source/platform/scroll/ScrollerSizeMetrics.h
new file mode 100644
index 0000000000000000000000000000000000000000..c9ebb24b51a8c63d700ef40f129b5c9223d3db98
--- /dev/null
+++ b/third_party/WebKit/Source/platform/scroll/ScrollerSizeMetrics.h
@@ -0,0 +1,15 @@
+// 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 ScrollerSizeMetrics_h
+#define ScrollerSizeMetrics_h
+
+#include "cc/input/scroller_size_metrics.h"
+
+namespace blink {
+using cc::kScrollerSizeLargestBucket;
+using cc::kScrollerSizeBucketCount;
+}
+
+#endif  // ScrollerSizeMetrics_h