Remove content/public/plugin and chrome/plugin

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 19 matching lines @@
   "content_main_runner.h",
   "sandbox_helper_win.h",
 ]
 
 public_app_shared_deps = [
   "//base",
   "//base:i18n",
   "//content:export",
   "//content/public/common:common_sources",
   "//content/public/gpu:gpu_sources",
-  "//content/public/plugin:plugin_sources",
   "//content/public/renderer:renderer_sources",
   "//content/public/utility:utility_sources",
 ]
 
 if (is_component_build) {
   source_set("both_sources") {
     # Only the main content shared library can pull this in.
     visibility = [ "//content:content" ]
 
     sources = public_app_shared_sources
@@ skipping 83 matching lines @@
         ":both",
       ]
     }
     group("child") {
       deps = [
         ":both",
       ]
     }
   }
 }