ui + mus: Split ContextFactory into ContextFactory(Client) and ContextFactoryPrivate

ui/compositor/test/test_compositor_host_ozone.cc

Index: ui/compositor/test/test_compositor_host_ozone.cc
diff --git a/ui/compositor/test/test_compositor_host_ozone.cc b/ui/compositor/test/test_compositor_host_ozone.cc
index 281c6fdbb5bb47a801c187b6cbca600a4a7b02bc..18e5f821b644e4f6cea97e327e1c4941a988bf8a 100644
--- a/ui/compositor/test/test_compositor_host_ozone.cc
+++ b/ui/compositor/test/test_compositor_host_ozone.cc
@@ -39,7 +39,9 @@ TestCompositorHostOzone::TestCompositorHostOzone(
     const gfx::Rect& bounds,
     ui::ContextFactory* context_factory)
     : bounds_(bounds),
-      compositor_(context_factory, base::ThreadTaskRunnerHandle::Get()) {}
+      compositor_(context_factory,
+                  nullptr,
+                  base::ThreadTaskRunnerHandle::Get()) {}
 
 TestCompositorHostOzone::~TestCompositorHostOzone() {}