Introduce painted-device-scale-factor and use it when --enable-use-zoom-for-dsf is specified.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 9f1efdcdadbd9853f533b60d065aee811459e38f..30cc14c5e9623882760c7cad7dac925f1d892fd1 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1511,7 +1511,9 @@ void LayerTreeHostImpl::OnCanDrawStateChangedForTree() {
 
 CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
   CompositorFrameMetadata metadata;
-  metadata.device_scale_factor = active_tree_->device_scale_factor();
+  metadata.device_scale_factor = active_tree_->painted_device_scale_factor() *
+                                 active_tree_->device_scale_factor();
+
   metadata.page_scale_factor = active_tree_->current_page_scale_factor();
   metadata.scrollable_viewport_size = active_tree_->ScrollableViewportSize();
   metadata.root_layer_size = active_tree_->ScrollableSize();