Set device scale factor in CompositorFrame and scale frame size in WS.

services/ui/ws/frame_generator.cc

Index: services/ui/ws/frame_generator.cc
diff --git a/services/ui/ws/frame_generator.cc b/services/ui/ws/frame_generator.cc
index d9774da887dd264bced6fe27dd6dde015ea12447..6d02f41ba9014e55c23970448ec9dfa436134bed 100644
--- a/services/ui/ws/frame_generator.cc
+++ b/services/ui/ws/frame_generator.cc
@@ -152,6 +152,7 @@ cc::CompositorFrame FrameGenerator::GenerateCompositorFrame(
                  cc::FilterOperations() /* background_filters */);
     frame.render_pass_list.push_back(std::move(invert_pass));
   }
+  frame.metadata.device_scale_factor = device_scale_factor_;
 
   return frame;
 }