Make ui::Layer use the cc:LayerTreeHost scale factor directly

ui/aura/window_unittest.cc

Index: ui/aura/window_unittest.cc
diff --git a/ui/aura/window_unittest.cc b/ui/aura/window_unittest.cc
index c0bb6a56a289bcab2ec67866fa586192dd5b2f6a..5e08a170da097f9d34b11acccb75a0bce6ed295e 100644
--- a/ui/aura/window_unittest.cc
+++ b/ui/aura/window_unittest.cc
@@ -1905,7 +1905,6 @@ TEST_F(WindowTest, RecreateLayer) {
   w.SetBounds(gfx::Rect(0, 0, 100, 100));
 
   ui::Layer* layer = w.layer();
-  layer->set_scale_content(false);
   layer->SetVisible(false);
   layer->SetMasksToBounds(true);
 
@@ -1915,7 +1914,6 @@ TEST_F(WindowTest, RecreateLayer) {
   scoped_ptr<ui::Layer> old_layer(w.RecreateLayer());
   layer = w.layer();
   EXPECT_EQ(ui::LAYER_SOLID_COLOR, layer->type());
-  EXPECT_FALSE(layer->scale_content());
   EXPECT_FALSE(layer->visible());
   EXPECT_EQ(1u, layer->children().size());
   EXPECT_TRUE(layer->GetMasksToBounds());