Convert enable_plugins to a buildflag header.

chrome/browser/renderer_host/chrome_render_message_filter.h

Index: chrome/browser/renderer_host/chrome_render_message_filter.h
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.h b/chrome/browser/renderer_host/chrome_render_message_filter.h
index afb9538a0af45ad90b8de0ec0a22bb7baae38298..40175c713cb291ff8b8daaa2a2adc2a5afe382ef 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.h
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.h
@@ -13,6 +13,7 @@
 #include "base/sequenced_task_runner_helpers.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "extensions/features/features.h"
+#include "ppapi/features/features.h"
 
 class GURL;
 class Profile;
@@ -123,7 +124,7 @@ class ChromeRenderMessageFilter : public content::BrowserMessageFilter {
                         const GURL& top_origin_url,
                         const base::string16& name,
                         bool* allowed);
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   void OnIsCrashReportingEnabled(bool* enabled);
 #endif