Revert of Establish MojoChildConnection from BrowserChildProcessHostImpl

content/public/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.
 
 # App different than the regular content subcomponents (see comments in
 # //content/BUILD.gn) because it has to support the browser/child process split
 # (the "both" target include both browser and child process files and is used
 # for testing).
 #
 # In non-component mode, browser, child, and both all follow the same structure:
@@ skipping 168 matching lines @@
     "//services/user:manifest",
   ]
 }
 
 service_manifest("gpu_manifest") {
   type = "exe"
   name = "content_gpu"
   source = "mojo/content_gpu_manifest.json"
 }
 
-service_manifest("plugin_manifest") {
-  type = "exe"
-  name = "content_plugin"
-  source = "mojo/content_plugin_manifest.json"
-}
-
 service_manifest("renderer_manifest") {
   type = "exe"
   name = "content_renderer"
   source = "mojo/content_renderer_manifest.json"
 }
 
 service_manifest("utility_manifest") {
   type = "exe"
   name = "content_utility"
   source = "mojo/content_utility_manifest.json"
 }