Improve scroll performance on Windows 10 with high precision touchpads.

content/browser/renderer_host/legacy_render_widget_host_win.h

 // Copyright (c) 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_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_
 #define CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_
 
 #include <atlbase.h>
 #include <atlwin.h>
 #include <atlcrack.h>
 #include <oleacc.h>
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/win/scoped_comptr.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/geometry/rect.h"
 
+namespace gfx {
+namespace win {
+class DirectManipulationHelper;
+}  // namespace win
+}  // namespace gfx
+
 namespace ui {
 class WindowEventTarget;
 }
 
 namespace content {
 class RenderWidgetHostViewAura;
 
 // Reasons for the existence of this class outlined below:-
 // 1. Some screen readers expect every tab / every unique web content container
 //    to be in its own HWND with class name Chrome_RenderWidgetHostHWND.
@@ skipping 108 matching lines @@
   LRESULT OnNCCalcSize(UINT message, WPARAM w_param, LPARAM l_param);
   LRESULT OnSize(UINT message, WPARAM w_param, LPARAM l_param);
 
   base::win::ScopedComPtr<IAccessible> window_accessible_;
 
   // Set to true if we turned on mouse tracking.
   bool mouse_tracking_enabled_;
 
   RenderWidgetHostViewAura* host_;
 
+  // This class provides functionality to register the legacy window as a
+  // Direct Manipulation consumer. This allows us to support smooth scroll
+  // in Chrome on Windows 10.
+  scoped_ptr<gfx::win::DirectManipulationHelper> direct_manipulation_helper_;
+
   DISALLOW_COPY_AND_ASSIGN(LegacyRenderWidgetHostHWND);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_LEGACY_RENDER_WIDGET_HOST_WIN_H_