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 7bfe81b84dc5367087310d2bd1aa303a42fbd1f0..6368063de62ba082cd5dcf5d12774ae929c76f27 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1507,7 +1507,12 @@ void LayerTreeHostImpl::OnCanDrawStateChangedForTree() {
 
 CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
   CompositorFrameMetadata metadata;
-  metadata.device_scale_factor = active_tree_->device_scale_factor();
+  float metadata_device_scale_factor =
+      active_tree_->painted_device_scale_factor() > 0.0f

[danakj, 2015/10/22 23:15:29]

if it defaults to one you dont need an if here. you can just multiply them
together?

[oshima, 2015/10/23 18:05:36]

Done.

+          ? active_tree_->painted_device_scale_factor()
+          : active_tree_->device_scale_factor();
+
+  metadata.device_scale_factor = metadata_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();