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

services/ui/surfaces/display_compositor.cc

Index: services/ui/surfaces/display_compositor.cc
diff --git a/services/ui/surfaces/display_compositor.cc b/services/ui/surfaces/display_compositor.cc
index 772fbd009153230795c5c4144ad74681462bcdaf..52e0bc9ffdcf588e455a006f12f21c451eebcf85 100644
--- a/services/ui/surfaces/display_compositor.cc
+++ b/services/ui/surfaces/display_compositor.cc
@@ -246,6 +246,7 @@ void DisplayCompositor::OnSurfaceCreated(const cc::SurfaceId& surface_id,
                                          const gfx::Size& frame_size,
                                          float device_scale_factor) {
   DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_GT(device_scale_factor, 0.0f);
   // We can get into a situation where multiple CompositorFrames arrive for a
   // CompositorFrameSink before the DisplayCompositorClient can add any
   // references for the frame. When the second frame with a new size arrives,