Use actual value of display scale factor from GetMonitorScaleFactor().

ui/aura/window_tree_host.cc

 // Copyright (c) 2013 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.h"
 
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/cursor_client.h"
@@ skipping 16 matching lines @@
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/icc_profile.h"
 
 namespace aura {
 
 const char kWindowTreeHostForAcceleratedWidget[] =
     "__AURA_WINDOW_TREE_HOST_ACCELERATED_WIDGET__";
 
-float GetDeviceScaleFactorFromDisplay(Window* window) {
-  display::Display display =
-      display::Screen::GetScreen()->GetDisplayNearestWindow(window);
-  DCHECK(display.is_valid());
-  return display.device_scale_factor();
+float GetDeviceScaleFactorFromScreen(Window* window) {
+  return display::Screen::GetScreen()->GetScaleFactorForWindow(window);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WindowTreeHost, public:
 
 WindowTreeHost::~WindowTreeHost() {
   DCHECK(!compositor_) << "compositor must be destroyed before root window";
   if (owned_input_method_) {
     delete input_method_;
     input_method_ = nullptr;
   }
 }
 
 // static
 WindowTreeHost* WindowTreeHost::GetForAcceleratedWidget(
     gfx::AcceleratedWidget widget) {
   return reinterpret_cast<WindowTreeHost*>(
       ui::ViewProp::GetValue(widget, kWindowTreeHostForAcceleratedWidget));
 }
 
 void WindowTreeHost::InitHost() {
   InitCompositor();
   UpdateRootWindowSize(GetBounds().size());
   Env::GetInstance()->NotifyHostInitialized(this);
   window()->Show();
 }
 
 void WindowTreeHost::InitCompositor() {
-  compositor_->SetScaleAndSize(GetDeviceScaleFactorFromDisplay(window()),
+  compositor_->SetScaleAndSize(GetDeviceScaleFactorFromScreen(window()),
                                GetBounds().size());
   compositor_->SetRootLayer(window()->layer());
   compositor_->SetDisplayColorSpace(
       GetICCProfileForCurrentDisplay().GetColorSpace());
 }
 
 void WindowTreeHost::AddObserver(WindowTreeHostObserver* observer) {
   observers_.AddObserver(observer);
 }
 
@@ skipping 189 matching lines @@
 
 void WindowTreeHost::OnHostMoved(const gfx::Point& new_location) {
   TRACE_EVENT1("ui", "WindowTreeHost::OnHostMoved",
                "origin", new_location.ToString());
 
   for (WindowTreeHostObserver& observer : observers_)
     observer.OnHostMoved(this, new_location);
 }
 
 void WindowTreeHost::OnHostResized(const gfx::Size& new_size) {
+  LOG(ERROR) << "WindowTreeHost::OnHostResized(" << new_size.ToString()
+             << ", DPI = " << GetDeviceScaleFactorFromScreen(window()) << ")";
+
   gfx::Size adjusted_size(new_size);
   adjusted_size.Enlarge(output_surface_padding_.width(),
                         output_surface_padding_.height());
   // The compositor should have the same size as the native root window host.
   // Get the latest scale from display because it might have been changed.
-  compositor_->SetScaleAndSize(GetDeviceScaleFactorFromDisplay(window()),
+  compositor_->SetScaleAndSize(GetDeviceScaleFactorFromScreen(window()),
                                adjusted_size);
 
   gfx::Size layer_size = GetBounds().size();
   // The layer, and the observers should be notified of the
   // transformed size of the root window.
   UpdateRootWindowSize(layer_size);
   for (WindowTreeHostObserver& observer : observers_)
     observer.OnHostResized(this);
 }
 
@@ skipping 37 matching lines @@
   client::CursorClient* cursor_client = client::GetCursorClient(window());
   if (cursor_client) {
     const display::Display& display =
         display::Screen::GetScreen()->GetDisplayNearestWindow(window());
     cursor_client->SetDisplay(display);
   }
   dispatcher()->OnCursorMovedToRootLocation(root_location);
 }
 
 }  // namespace aura