Introduce Display Compositor mojo interface. Use InProcessContextProvider.

services/ui/ws/platform_display_default.cc

Index: services/ui/ws/platform_display_default.cc
diff --git a/services/ui/ws/platform_display_default.cc b/services/ui/ws/platform_display_default.cc
index 6a14cca1cf13455235d18f2115b70bd0ef379998..41d40ca8f519e1274b53693b0c2ce0958acaa0b4 100644
--- a/services/ui/ws/platform_display_default.cc
+++ b/services/ui/ws/platform_display_default.cc
@@ -129,11 +129,6 @@ FrameGenerator* PlatformDisplayDefault::GetFrameGenerator() {
   return frame_generator_.get();
 }
 
-void PlatformDisplayDefault::OnGpuChannelEstablished(
-    scoped_refptr<gpu::GpuChannelHost> channel) {
-  frame_generator_->OnGpuChannelEstablished(channel);
-}
-
 bool PlatformDisplayDefault::UpdateViewportMetrics(
     const display::ViewportMetrics& metrics) {
   if (metrics_ == metrics)