Simplify calls for scale factor

ui/aura/window_tree_host_platform.cc

 // Copyright 2015 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/aura/window_tree_host_platform.h"
 
 #include <utility>
 
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_port.h"
+#include "ui/base/layout.h"
 #include "ui/compositor/compositor.h"
-#include "ui/display/display.h"
-#include "ui/display/screen.h"
 #include "ui/events/event.h"
 
 #if defined(OS_ANDROID)
 #include "ui/platform_window/android/platform_window_android.h"
 #endif
 
 #if defined(USE_OZONE)
 #include "ui/ozone/public/ozone_platform.h"
 #endif
 
@@ skipping 101 matching lines @@
     const gfx::Point& location_in_pixels) {
   platform_window_->MoveCursorTo(location_in_pixels);
 }
 
 void WindowTreeHostPlatform::OnCursorVisibilityChangedNative(bool show) {
   NOTIMPLEMENTED();
 }
 
 void WindowTreeHostPlatform::OnBoundsChanged(const gfx::Rect& new_bounds) {
   float current_scale = compositor()->device_scale_factor();
-  float new_scale = display::Screen::GetScreen()
-                        ->GetDisplayNearestWindow(window())
-                        .device_scale_factor();
+  float new_scale = ui::GetScaleFactorForNativeView(window());
   gfx::Rect old_bounds = bounds_;
   bounds_ = new_bounds;
   if (bounds_.origin() != old_bounds.origin()) {
     OnHostMovedInPixels(bounds_.origin());
   }
   if (bounds_.size() != old_bounds.size() || current_scale != new_scale) {
     OnHostResizedInPixels(bounds_.size());
   }
 }
 
@@ skipping 38 matching lines @@
   DCHECK_EQ(widget, widget_);
   widget_ = gfx::kNullAcceleratedWidget;
 }
 
 void WindowTreeHostPlatform::OnActivationChanged(bool active) {
   if (active)
     OnHostActivated();
 }
 
 }  // namespace aura