Convert offscreen canvas to use FrameSinkManagerHost.

ui/compositor/test/in_process_context_factory.cc

Index: ui/compositor/test/in_process_context_factory.cc
diff --git a/ui/compositor/test/in_process_context_factory.cc b/ui/compositor/test/in_process_context_factory.cc
index aecb9b792c2f1a2993f2c0c00bf0d7080ee97b28..70b07a5a0577990da02c910431c22331dfa53738 100644
--- a/ui/compositor/test/in_process_context_factory.cc
+++ b/ui/compositor/test/in_process_context_factory.cc
@@ -296,6 +296,11 @@ cc::SurfaceManager* InProcessContextFactory::GetSurfaceManager() {
   return surface_manager_;
 }
 
+cc::mojom::DisplayCompositor* InProcessContextFactory::GetDisplayCompositor() {
+  NOTIMPLEMENTED();
+  return nullptr;
+}
+
 void InProcessContextFactory::SetDisplayVisible(ui::Compositor* compositor,
                                                 bool visible) {
   if (!per_compositor_data_.count(compositor))