Restructure public side of view_manager service.

mojo/services/view_manager/public/cpp/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.
 
-source_set("view_manager") {
+source_set("cpp") {
   sources = [
     "lib/view.cc",
     "lib/view_manager_client_factory.cc",
     "lib/view_manager_client_impl.cc",
     "lib/view_manager_client_impl.h",
     "lib/view_manager_context.cc",
     "lib/view_observer.cc",
     "lib/view_private.cc",
     "lib/view_private.h",
     "view.h",
@@ skipping 12 matching lines @@
   ]
   deps = [
     "//base",
     "//mojo/public/c/gles2:headers",
     "//mojo/public/cpp/application",
     "//mojo/public/cpp/bindings:bindings",
     "//mojo/public/interfaces/application",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/input_events:input_events",
     "//mojo/services/public/interfaces/surfaces:surface_id",
-    "//mojo/services/public/interfaces/view_manager",
+    "//mojo/services/view_manager/public/interfaces",
     "//mojo/services/window_manager/public/interfaces",
   ]
 }
 
 source_set("common") {
   sources = [
     "types.h",
   ]
 }