Fix //content/plugin ax_enums gn build flake (take 2)

content/plugin/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.
 
 import("//build/config/features.gni")
 
 # This is the NPAPI plugin process. It isn't used on Linux.
 if (enable_plugins && !is_linux) {
   source_set("plugin") {
     # Only the public target should depend on this. All other targets (even
@@ skipping 14 matching lines @@
       "webplugin_delegate_stub.cc",
       "webplugin_delegate_stub.h",
       "webplugin_proxy.cc",
       "webplugin_proxy.h",
     ]
 
     configs += [ "//content:content_implementation" ]
 
     deps = [
       "//content:export",
+      "//content/public/common:common_sources",
       "//mojo/application/public/interfaces",
       "//skia",
       "//third_party/npapi",
       "//third_party/WebKit/public:blink",
     ]
   }
 } else {
   # This way it can be unconditionally depended on.
   group("plugin") {
   }
 }