Move //sky/compositor to //sky/viewer/compositor

sky/viewer/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")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojo_native_application("viewer") {
   output_name = "sky_viewer"
 
@@ skipping 32 matching lines @@
     "//mojo/services/content_handler/public/interfaces",
     "//mojo/services/gpu/public/interfaces",
     "//mojo/services/input_events/public/interfaces",
     "//mojo/services/navigation/public/interfaces",
     "//mojo/services/network/public/interfaces",
     "//mojo/services/service_registry/public/interfaces",
     "//mojo/services/surfaces/public/interfaces",
     "//mojo/services/view_manager/public/cpp",
     "//mojo/services/view_manager/public/interfaces",
     "//skia",
-    "//sky/compositor",
     "//sky/engine",
     "//sky/engine/tonic",
     "//sky/services/platform",
     "//sky/services/testing:bindings",
     "//sky/shell/dart",
+    "//sky/viewer/compositor",
     "//third_party/icu",
     "//ui/events",
     "//url",
   ]
 }