Convert enable_plugins to a buildflag header.

components/strings/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/locales.gni")
+import("//ppapi/features/features.gni")
 import("//tools/grit/grit_rule.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
   android_components_strings_java_resources = [
     "java/res/values-am/components_strings.xml",
     "java/res/values-ar/components_strings.xml",
     "java/res/values-bg/components_strings.xml",
     "java/res/values-ca/components_strings.xml",
     "java/res/values-cs/components_strings.xml",
@@ skipping 43 matching lines @@
   public_deps = [
     ":components_chromium_strings",
     ":components_google_chrome_strings",
     ":components_locale_settings",
     ":components_strings",
   ]
 }
 
 grit("components_strings") {
   source = "../components_strings.grd"
+  defines = [ "enable_plugins=$enable_plugins" ]
+
   outputs = [
     "grit/components_strings.h",
   ]
   foreach(locale, locales_with_fake_bidi) {
     outputs += [ "components_strings_$locale.pak" ]
   }
 
   if (is_android) {
     outputs += android_components_strings_java_resources
   }
@@ skipping 98 matching lines @@
     grit_output_dir = "$root_gen_dir/components/strings/java/res"
     generated_files =
         rebase_path(android_components_locale_settings_java_resources,
                     "java/res",
                     ".")
     deps = [
       ":components_locale_settings",
     ]
   }
 }