Revert of Disable scrollbar snapback on desktop Linux

content/renderer/webscrollbarbehavior_impl_gtkoraura.h

+// 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.
+
+#ifndef CONTENT_RENDERER_WEBSCROLLBARBEHAVIOR_IMPL_GTKORAURA_H_
+#define CONTENT_RENDERER_WEBSCROLLBARBEHAVIOR_IMPL_GTKORAURA_H_
+
+#include "third_party/WebKit/public/platform/WebScrollbarBehavior.h"
+
+namespace content {
+
+class WebScrollbarBehaviorImpl : public blink::WebScrollbarBehavior {
+ public:
+  bool shouldCenterOnThumb(blink::WebPointerProperties::Button mouseButton,
+                           bool shiftKeyPressed,
+                           bool altKeyPressed) override;
+  bool shouldSnapBackToDragOrigin(const blink::WebPoint& eventPoint,
+                                  const blink::WebRect& scrollbarRect,
+                                  bool isHorizontal) override;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_WEBSCROLLBARBEHAVIOR_IMPL_GTKORAURA_H_