Add a simple compositor for Sky

examples/sky_compositor_app/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/mojo_application.gni")
 
-mojo_native_application("nesting_app") {
+mojo_native_application("sky_compositor_app") {
   sources = [
-    "nesting_app.cc"
+    "sky_compositor_app.cc",
   ]
 
   deps = [
     "//base",
-    "//examples/bitmap_uploader",
-    "//examples/window_manager:bindings",
     "//mojo/application",
+    "//mojo/common",
+    "//mojo/converters/geometry",
+    "//mojo/environment:chromium",
     "//mojo/public/c/system:for_shared_library",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/environment",
+    "//mojo/public/cpp/system",
     "//mojo/public/cpp/utility",
     "//mojo/services/public/cpp/view_manager",
     "//mojo/services/public/interfaces/geometry",
-    "//mojo/services/public/interfaces/navigation",
     "//skia",
+    "//sky/compositor",
     "//ui/gfx/geometry",
-    "//ui/gl",
-    "//url",
   ]
 }