Ensure that trackpad and trackpoint scrolling works on Windows desktop Aura with legacy trackpad dr…

ui/views/widget/widget_hwnd_utils.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/widget/widget_hwnd_utils.h"
 
 #include <dwmapi.h>
 
 #include "base/command_line.h"
 #include "base/win/windows_version.h"
@@ skipping 115 matching lines @@
     case Widget::InitParams::TYPE_POPUP:
       *style |= WS_POPUP;
       *ex_style |= WS_EX_TOOLWINDOW;
       break;
     case Widget::InitParams::TYPE_MENU:
       *style |= WS_POPUP;
       break;
     default:
       NOTREACHED();
   }
+
+#if defined(USE_AURA)
+  // Certain trackpad drivers on Windows have bugs where in they don't generate
+  // WM_MOUSEWHEEL messages for the trackpoint and trackpad scrolling gestures
+  // unless there is an entry for Chrome with the class name of the Window.
+  // These drivers check if the window under the trackpoint has the WS_VSCROLL/
+  // WS_HSCROLL style and if yes they generate the legacy WM_VSCROLL/WM_HSCROLL
+  // messages. We add these styles to ensure that trackpad/trackpoint scrolling
+  // work.
+  if (!params.child)
+    *style |= WS_VSCROLL | WS_HSCROLL;
+#endif
 }
 
 }  // namespace
 
 bool DidClientAreaSizeChange(const WINDOWPOS* window_pos) {
   return !(window_pos->flags & SWP_NOSIZE) ||
          window_pos->flags & SWP_FRAMECHANGED;
 }
 
 void ConfigureWindowStyles(
     HWNDMessageHandler* handler,
     const Widget::InitParams& params,
     WidgetDelegate* widget_delegate,
     internal::NativeWidgetDelegate* native_widget_delegate) {
   // Configure the HWNDMessageHandler with the appropriate
   DWORD style = 0;
   DWORD ex_style = 0;
   DWORD class_style = 0;
   CalculateWindowStylesFromInitParams(params, widget_delegate,
                                       native_widget_delegate, &style, &ex_style,
                                       &class_style);
   handler->set_initial_class_style(class_style);
   handler->set_window_style(handler->window_style() | style);
   handler->set_window_ex_style(handler->window_ex_style() | ex_style);
 }
 
 }  // namespace views