Move enable extensions define to a build flag.

chrome/renderer/chrome_render_view_observer.h

Index: chrome/renderer/chrome_render_view_observer.h
diff --git a/chrome/renderer/chrome_render_view_observer.h b/chrome/renderer/chrome_render_view_observer.h
index 6d0e671bda415ba00428d88f2a178a300c98e53d..6f55ba9b48364689e66f50de2216e2d7af3ae955 100644
--- a/chrome/renderer/chrome_render_view_observer.h
+++ b/chrome/renderer/chrome_render_view_observer.h
@@ -14,6 +14,7 @@
 #include "build/build_config.h"
 #include "content/public/common/browser_controls_state.h"
 #include "content/public/renderer/render_view_observer.h"
+#include "extensions/features/features.h"
 #include "url/gurl.h"
 
 class ContentSettingsObserver;
@@ -49,7 +50,7 @@ class ChromeRenderViewObserver : public content::RenderViewObserver {
 #if !defined(OS_ANDROID)
   void OnWebUIJavaScript(const base::string16& javascript);
 #endif
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   void OnSetVisuallyDeemphasized(bool deemphasized);
 #endif
 #if defined(OS_ANDROID)