Convert enable_plugins to a buildflag header.

chrome/common/render_messages.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.
 
 // Multiply-included file, no traditional include guard.
 #include <stdint.h>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
@@ skipping 574 matching lines @@
 IPC_MESSAGE_ROUTED2(ChromeViewHostMsg_SearchBoxUndoMostVisitedDeletion,
                     int /* page_seq_no */,
                     GURL /* url */)
 
 // Tells the renderer a list of URLs which should be bounced back to the browser
 // process so that they can be assigned to an Instant renderer.
 IPC_MESSAGE_CONTROL2(ChromeViewMsg_SetSearchURLs,
                      std::vector<GURL> /* search_urls */,
                      GURL /* new_tab_page_url */)
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 // Sent by the renderer to check if crash reporting is enabled.
 IPC_SYNC_MESSAGE_CONTROL0_1(ChromeViewHostMsg_IsCrashReportingEnabled,
                             bool /* enabled */)
 #endif
 
 // Sent by the renderer to indicate that a fields trial has been activated.
 IPC_MESSAGE_CONTROL1(ChromeViewHostMsg_FieldTrialActivated,
                      std::string /* name */)