ui: Make gfx::Size::Scale() mutate the class. Add gfx::ScaleSize() similar to Rect/Point.

ui/gfx/display.cc

Index: ui/gfx/display.cc
diff --git a/ui/gfx/display.cc b/ui/gfx/display.cc
index e647f650603ff777e9a2c46931e5e11c7d3c645a..ef3f250a483d113770958e5003f37b2d1507044b 100644
--- a/ui/gfx/display.cc
+++ b/ui/gfx/display.cc
@@ -89,7 +89,7 @@ void Display::SetScaleAndBounds(
   bounds_in_pixel_ = bounds_in_pixel;
 #endif
   bounds_ = gfx::Rect(gfx::ToFlooredSize(
-      bounds_in_pixel.size().Scale(1.0f / device_scale_factor_)));
+      gfx::ScaleSize(bounds_in_pixel.size(), 1.0f / device_scale_factor_)));
   UpdateWorkAreaFromInsets(insets);
 }
 
@@ -109,7 +109,7 @@ void Display::UpdateWorkAreaFromInsets(const gfx::Insets& insets) {
 }
 
 gfx::Size Display::GetSizeInPixel() const {
-  return gfx::ToFlooredSize(size().Scale(device_scale_factor_));
+  return gfx::ToFlooredSize(gfx::ScaleSize(size(), device_scale_factor_));
 }
 
 std::string Display::ToString() const {