Convert enable_plugins to a buildflag header.

content/common/plugin_list.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_COMMON_PLUGIN_LIST_H_
 #define CONTENT_COMMON_PLUGIN_LIST_H_
 
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "content/public/common/webplugininfo.h"
+#include "ppapi/features/features.h"
 
-#if !defined(ENABLE_PLUGINS)
+#if !BUILDFLAG(ENABLE_PLUGINS)
 #error "Plugins should be enabled"
 #endif
 
 class GURL;
 
 namespace content {
 
 // The PluginList is responsible for loading our NPAPI based plugins. It does
 // so in whatever manner is appropriate for the platform. On Windows, it loads
 // plugins from a known directory by looking for DLLs which start with "NP",
@@ skipping 141 matching lines @@
   // Need synchronization for the above members since this object can be
   // accessed on multiple threads.
   base::Lock lock_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginList);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_PLUGIN_LIST_H_