Move sky_viewer into services/sky

sky/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.
 
 group("sky") {
   testonly = true
 
   deps = [
     "//services/debugger",
     "//sky/engine/platform:platform_unittests",
     "//sky/engine/wtf:unittests",
     "//sky/sdk/example",
     "//sky/tools/imagediff",
     "//sky/tools/packager($host_toolchain)",
-    "//sky/viewer",
     ":sky_dev",
   ]
 
   if (!is_android) {
     deps += [ "//third_party/mesa:osmesa" ]
   }
 }
 
 group("sky_dev") {
   testonly = true
 
   deps = [
     "//sky/sdk",
   ]
 
   if (is_android) {
     deps += [ "//sky/services/activity" ]
   }
 
   if (is_linux) {
     deps += [ "//sky/shell" ]
   }
 }