Remove the enable_themes build flag and define.

chrome/browser/ui/webui/ntp/new_tab_ui.cc

Index: chrome/browser/ui/webui/ntp/new_tab_ui.cc
diff --git a/chrome/browser/ui/webui/ntp/new_tab_ui.cc b/chrome/browser/ui/webui/ntp/new_tab_ui.cc
index 8a9faccb7bf70b89846d67947d3771a600dc195f..ddc42c4d73ac32c7af3624f97b8f625cbac08bbe 100644
--- a/chrome/browser/ui/webui/ntp/new_tab_ui.cc
+++ b/chrome/browser/ui/webui/ntp/new_tab_ui.cc
@@ -17,6 +17,7 @@
 #include "chrome/browser/ui/webui/ntp/favicon_webui_handler.h"
 #include "chrome/browser/ui/webui/ntp/ntp_resource_cache.h"
 #include "chrome/browser/ui/webui/ntp/ntp_resource_cache_factory.h"
+#include "chrome/browser/ui/webui/theme_handler.h"
 #include "chrome/common/url_constants.h"
 #include "components/bookmarks/common/bookmark_pref_names.h"
 #include "components/prefs/pref_service.h"
@@ -30,10 +31,6 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "url/gurl.h"
 
-#if defined(ENABLE_THEMES)
-#include "chrome/browser/ui/webui/theme_handler.h"
-#endif
-
 using content::BrowserThread;
 using content::WebUIController;
 
@@ -74,10 +71,8 @@ NewTabUI::NewTabUI(content::WebUI* web_ui)
       web_ui->AddMessageHandler(new AppLauncherHandler(service));
   }
 
-#if defined(ENABLE_THEMES)
   if (!profile->IsGuestSession())
     web_ui->AddMessageHandler(new ThemeHandler());
-#endif
 
   std::unique_ptr<NewTabHTMLSource> html_source(
       new NewTabHTMLSource(profile->GetOriginalProfile()));