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 55c5419e10464a654ae14e8c737b3f2a93d2c3c6..5ba20d1dd39db8ee6fd27da7f7a93e6bfd6d2956 100644
--- a/services/ui/ws/frame_generator.cc
+++ b/services/ui/ws/frame_generator.cc
@@ -149,6 +149,7 @@ cc::CompositorFrame FrameGenerator::GenerateCompositorFrame(
                  gfx::PointF() /* filters_origin */);
     frame.render_pass_list.push_back(std::move(invert_pass));
   }
+  frame.metadata.device_scale_factor = device_scale_factor_;
 
   return frame;
 }