Convert enable_plugins to a buildflag header.

content/utility/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("//media/media_options.gni")
 
 source_set("utility") {
   # Only the public target should depend on this. All other targets (even
   # internal content ones other than test) should depend on the public one.
   visibility = [
@@ skipping 16 matching lines @@
   configs += [ "//content:content_implementation" ]
 
   deps = [
     "//base",
     "//content:export",
     "//content/child",
     "//content/public/child:child_sources",
     "//content/public/common:common_sources",
     "//mojo/common",
     "//mojo/public/cpp/bindings",
+    "//ppapi/features",
     "//sandbox",
     "//services/service_manager",
     "//services/service_manager/public/cpp",
     "//services/service_manager/public/interfaces",
     "//third_party/WebKit/public:blink_headers",
     "//third_party/WebKit/public:mojo_bindings",
     "//url",
   ]
 
   if (mojo_media_host == "utility") {
     deps += [ "//media/mojo/services" ]
   }
 }
 
 # See comment at the top of //content/BUILD.gn for how this works.
 group("for_content_tests") {
   visibility = [ "//content/test/*" ]
   if (!is_component_build) {
     public_deps = [
       ":utility",
     ]
   }
 }