Introduce Display Compositor mojo interface. Use InProcessContextProvider.

services/ui/gpu/interfaces/gpu_service_internal.mojom

Index: services/ui/gpu/interfaces/gpu_service_internal.mojom
diff --git a/services/ui/gpu/interfaces/gpu_service_internal.mojom b/services/ui/gpu/interfaces/gpu_service_internal.mojom
index 18474844f0bb5a4b94b9e77e8800d7fb3541dee8..93451a4765750245911b2588b742e0df593be03b 100644
--- a/services/ui/gpu/interfaces/gpu_service_internal.mojom
+++ b/services/ui/gpu/interfaces/gpu_service_internal.mojom
@@ -4,6 +4,7 @@
 
 module ui.mojom;
 
+import "cc/ipc/display_compositor.mojom";
 import "gpu/ipc/common/gpu_info.mojom";
 import "gpu/ipc/common/surface_handle.mojom";
 import "gpu/ipc/common/sync_token.mojom";
@@ -32,4 +33,9 @@ interface GpuServiceInternal {
   DestroyGpuMemoryBuffer(gfx.mojom.GpuMemoryBufferId id,
                          int32 client_id,
                          gpu.mojom.SyncToken sync_token);
+
+  // Tells the GPU process to create a display compositor.
+  CreateDisplayCompositor(
+    cc.mojom.DisplayCompositor& display_compositor,
+    cc.mojom.DisplayCompositorClient display_compositor_client);
 };