Introduce Display Compositor mojo interface. Use InProcessContextProvider.

services/ui/ws/window_tree.cc

Index: services/ui/ws/window_tree.cc
diff --git a/services/ui/ws/window_tree.cc b/services/ui/ws/window_tree.cc
index 8089988e2b745d814e311f675966806b18d67e55..165a27d48c3f8f2616af10c5ba38d9fa54aaf7e8 100644
--- a/services/ui/ws/window_tree.cc
+++ b/services/ui/ws/window_tree.cc
@@ -1370,8 +1370,8 @@ void WindowTree::AttachCompositorFrameSink(
     DVLOG(1) << "request to AttachCompositorFrameSink failed";
     return;
   }
-  window->CreateCompositorFrameSink(type, gfx::kNullAcceleratedWidget, nullptr,
-                                    nullptr, std::move(compositor_frame_sink),
+  window->CreateCompositorFrameSink(type, gfx::kNullAcceleratedWidget,
+                                    std::move(compositor_frame_sink),
                                     std::move(client));
 }