gfx: Make conversions from Size to SizeF be explicit.

ash/desktop_background/desktop_background_view.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 "ash/desktop_background/desktop_background_view.h"
 
 #include <limits>
 
 #include "ash/ash_export.h"
 #include "ash/desktop_background/desktop_background_controller.h"
@@ skipping 39 matching lines @@
     view->SetPaintToLayer(true);
   }
 
   // Overrides views::View.
   void Layout() override {
     gfx::Display display = Shell::GetScreen()->GetDisplayNearestWindow(
         GetWidget()->GetNativeView());
     DisplayManager* display_manager = Shell::GetInstance()->display_manager();
     DisplayInfo info = display_manager->GetDisplayInfo(display.id());
     float ui_scale = info.GetEffectiveUIScale();
-    gfx::SizeF pixel_size = display.size();
-    pixel_size.Scale(1.0f / ui_scale);
-    gfx::Size rounded_size = gfx::ToFlooredSize(pixel_size);
+    gfx::Size rounded_size =
+        gfx::ScaleToFlooredSize(display.size(), 1.f / ui_scale);
     DCHECK_EQ(1, child_count());
     views::View* child = child_at(0);
     child->SetBounds(0, 0, rounded_size.width(), rounded_size.height());
     gfx::Transform transform;
     // Apply RTL transform explicitly becacuse Views layer code
     // doesn't handle RTL.  crbug.com/458753.
     transform.Translate(-child->GetMirroredX(), 0);
     transform.Scale(ui_scale, ui_scale);
     child->SetTransform(transform);
   }
@@ skipping 174 matching lines @@
     // Disable animation if transition to login screen from an empty background.
     wm::SetWindowVisibilityAnimationTransition(
         desktop_widget->GetNativeView(), wm::ANIMATE_NONE);
   }
 
   desktop_widget->SetBounds(params.parent->bounds());
   return desktop_widget;
 }
 
 }  // namespace ash