Move enable extensions define to a build flag.

chrome/browser/renderer_host/chrome_navigation_ui_data.h

 // Copyright 2016 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_RENDERER_HOST_CHROME_NAVIGATION_UI_DATA_H_
 #define CHROME_BROWSER_RENDERER_HOST_CHROME_NAVIGATION_UI_DATA_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/public/browser/navigation_ui_data.h"
 #include "extensions/browser/extension_navigation_ui_data.h"
+#include "extensions/features/features.h"
 
 namespace content {
 class NavigationHandle;
 }
 
 // PlzNavigate
 // Contains data that is passed from the UI thread to the IO thread at the
 // beginning of each navigation. The class is instantiated on the UI thread,
 // then a copy created using Clone is passed to the content::ResourceRequestInfo
 // on the IO thread.
 class ChromeNavigationUIData : public content::NavigationUIData {
  public:
   ChromeNavigationUIData();
   explicit ChromeNavigationUIData(content::NavigationHandle* navigation_handle);
   ~ChromeNavigationUIData() override;
 
   // Creates a new ChromeNavigationUIData that is a deep copy of the original.
   // Any changes to the original after the clone is created will not be
   // reflected in the clone.  |extension_data_| is deep copied.
   std::unique_ptr<content::NavigationUIData> Clone() const override;
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   void SetExtensionNavigationUIData(
       std::unique_ptr<extensions::ExtensionNavigationUIData> extension_data);
 
   extensions::ExtensionNavigationUIData* GetExtensionNavigationUIData() const {
     return extension_data_.get();
   }
 #endif
 
  private:
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // Manages the lifetime of optional ExtensionNavigationUIData information.
   std::unique_ptr<extensions::ExtensionNavigationUIData> extension_data_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ChromeNavigationUIData);
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_CHROME_NAVIGATION_UI_DATA_H_