Convert enable_plugins to a buildflag header.

chrome/browser/content_settings/content_settings_browsertest.cc

 // 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.
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/scoped_feature_list.h"
 #include "build/build_config.h"
@@ skipping 327 matching lines @@
 
   ui_test_utils::NavigateToURL(browser(), test_url);
 
   content::WebContents* web_contents =
       browser()->tab_strip_model()->GetActiveWebContents();
 
   EXPECT_TRUE(TabSpecificContentSettings::FromWebContents(web_contents)->
       IsContentBlocked(CONTENT_SETTINGS_TYPE_COOKIES));
 }
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 class PepperContentSettingsSpecialCasesTest : public ContentSettingsTest {
  protected:
   void SetUpCommandLine(base::CommandLine* command_line) override {
     ASSERT_TRUE(ppapi::RegisterFlashTestPlugin(command_line));
 
 #if !defined(DISABLE_NACL)
     // Ensure NaCl can run.
     command_line->AppendSwitch(switches::kEnableNaCl);
 #endif
   }
@@ skipping 181 matching lines @@
 }
 #endif  // BUILDFLAG(ENABLE_PEPPER_CDMS) && defined(WIDEVINE_CDM_AVAILABLE)
 
 #if !defined(DISABLE_NACL)
 IN_PROC_BROWSER_TEST_F(PepperContentSettingsSpecialCasesJavaScriptBlockedTest,
                        NaCl) {
   RunJavaScriptBlockedTest("load_nacl_no_js.html", true);
 }
 #endif  // !defined(DISABLE_NACL)
 
-#endif  // defined(ENABLE_PLUGINS)
+#endif  // BUILDFLAG(ENABLE_PLUGINS)