Replace most uses of ViewManagerInitService with client lib ViewManager::Embed() to offer the same …

mojo/services/public/cpp/view_manager/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.
 
 # GYP version: mojo/mojo_services.gypi:mojo_view_manager_lib
 source_set("view_manager") {
   sources = [
     "lib/bitmap_uploader.cc",
     "lib/bitmap_uploader.h",
     "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",
     "view_manager.h",
     "view_manager_client_factory.h",
+    "view_manager_context.h",
     "view_manager_delegate.h",
     "view_observer.h",
     "window_manager_delegate.h",
   ]
 
   public_deps = [
     ":common",
     "//skia",
   ]
   deps = [
@@ skipping 23 matching lines @@
 
 source_set("common") {
   sources = [
     "ids.h",
     "types.h",
   ]
   public_deps = [
     "//base",
   ]
 }