Move enable extensions define to a build flag.

chrome/browser/ssl/ssl_blocking_page.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 CHROME_BROWSER_SSL_SSL_BLOCKING_PAGE_H_
 #define CHROME_BROWSER_SSL_SSL_BLOCKING_PAGE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/time/time.h"
 #include "chrome/browser/interstitials/security_interstitial_page.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ssl/ssl_cert_reporter.h"
 #include "components/certificate_reporting/error_report.h"
 #include "content/public/browser/certificate_request_result_type.h"
+#include "extensions/features/features.h"
 #include "net/ssl/ssl_info.h"
 #include "url/gurl.h"
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 namespace extensions {
 class ExperienceSamplingEvent;
 }
 #endif
 
 namespace policy {
 class PolicyTest_SSLErrorOverridingDisallowed_Test;
 }
 
 namespace security_interstitials {
@@ skipping 81 matching lines @@
   // expired.
   const bool expired_but_previously_allowed_;
 
   const std::unique_ptr<CertReportHelper> cert_report_helper_;
   const std::unique_ptr<security_interstitials::SSLErrorUI> ssl_error_ui_;
 
   DISALLOW_COPY_AND_ASSIGN(SSLBlockingPage);
 };
 
 #endif  // CHROME_BROWSER_SSL_SSL_BLOCKING_PAGE_H_