Do not scale ScrollEvent by device scale factor

ash/display/event_transformation_handler.cc

Index: ash/display/event_transformation_handler.cc
diff --git a/ash/display/event_transformation_handler.cc b/ash/display/event_transformation_handler.cc
index cb33891edf6bbd8261898723976780e840903dce..5f25e145c41401a43d22757fbfa6cc5a8dbf0c74 100644
--- a/ash/display/event_transformation_handler.cc
+++ b/ash/display/event_transformation_handler.cc
@@ -40,20 +40,17 @@ void EventTransformationHandler::OnScrollEvent(ui::ScrollEvent* event) {
   if (transformation_mode_ == TRANSFORM_NONE)
     return;
 
-  // Get the device scale factor and stack it on the final scale factor.
+  // It is unnecessary to scale the event for the device scale factor since
+  // the event locations etc. are already in DIP.
   gfx::Point point_in_screen(event->location());
   aura::Window* target = static_cast<aura::Window*>(event->target());
-  const float scale_at_target = ui::GetDeviceScaleFactor(target->layer());
-  float scale = scale_at_target;
-
-  // Apply some additional scaling if the display is non-integrated.
   wm::ConvertPointToScreen(target, &point_in_screen);
   const gfx::Display& display =
       Shell::GetScreen()->GetDisplayNearestPoint(point_in_screen);
-  if (!display.IsInternal())
-    scale *= kBoostForNonIntegrated;
 
-  event->Scale(scale);
+  // Apply some additional scaling if the display is non-integrated.
+  if (!display.IsInternal())
+    event->Scale(kBoostForNonIntegrated);
 }
 
 #if defined(OS_CHROMEOS)