Introduce Display Compositor mojo interface. Use InProcessContextProvider.

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index 3ab93974429d3dd07a6b98a31f7f031f92c3a086..3015363ef2da841c9d7c67d08b2467d6eab2a61c 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -55,11 +55,10 @@ WindowServer::WindowServer(WindowServerDelegate* delegate)
       next_wm_change_id_(0),
       gpu_proxy_(new GpuServiceProxy(this)),
       window_manager_window_tree_factory_set_(this, &user_id_tracker_),
-      display_compositor_client_binding_(this),
-      display_compositor_(new DisplayCompositor(
-          display_compositor_client_binding_.CreateInterfacePtrAndBind())) {
+      display_compositor_client_binding_(this) {
   user_id_tracker_.AddObserver(this);
   OnUserIdAdded(user_id_tracker_.active_id());
+  display_compositor_request_ = mojo::GetProxy(&display_compositor_);
 }
 
 WindowServer::~WindowServer() {
@@ -495,8 +494,6 @@ WindowTree* WindowServer::GetCurrentDragLoopInitiator() {
 }
 
 void WindowServer::OnDisplayReady(Display* display, bool is_first) {
-  if (gpu_channel_)
-    display->platform_display()->OnGpuChannelEstablished(gpu_channel_);
   if (is_first)
     delegate_->OnFirstDisplayReady();
 }
@@ -511,7 +508,7 @@ WindowManagerState* WindowServer::GetWindowManagerStateForUser(
       user_id);
 }
 
-ui::DisplayCompositor* WindowServer::GetDisplayCompositor() {
+cc::mojom::DisplayCompositor* WindowServer::GetDisplayCompositor() {
   return display_compositor_.get();
 }
 
@@ -744,12 +741,10 @@ void WindowServer::OnTransientWindowRemoved(ServerWindow* window,
   }
 }
 
-void WindowServer::OnGpuChannelEstablished(
-    scoped_refptr<gpu::GpuChannelHost> gpu_channel) {
-  gpu_channel_ = std::move(gpu_channel);
-  const std::set<Display*>& displays = display_manager()->displays();
-  for (auto* display : displays)
-    display->platform_display()->OnGpuChannelEstablished(gpu_channel_);
+void WindowServer::OnGpuServiceInitialized() {
+  gpu_proxy_->CreateDisplayCompositor(
+      std::move(display_compositor_request_),
+      display_compositor_client_binding_.CreateInterfacePtrAndBind());
   // TODO(kylechar): When gpu channel is removed, this can instead happen
   // earlier, after GpuServiceProxy::OnInitialized().
   delegate_->StartDisplayInit();