MacViews: Consolidate flags. Just use --secondary-ui-md to enable MacViews.

chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc

Index: chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc
diff --git a/chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc b/chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc
index 599e9a3fd73c207e4e17a6c5e2b2530109a6bd7a..54cebcb9853b1ec6d6cc5ddc5b874e95fcefcfe5 100644
--- a/chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc
+++ b/chrome/browser/ui/javascript_dialogs/javascript_dialog_mac.cc
@@ -5,11 +5,11 @@
 #include "chrome/browser/ui/javascript_dialogs/javascript_dialog.h"
 
 #include "chrome/browser/ui/blocked_content/app_modal_dialog_helper.h"
-#include "chrome/browser/ui/browser_dialogs.h"
 #include "chrome/browser/ui/javascript_dialogs/javascript_dialog_cocoa.h"
 #include "chrome/browser/ui/javascript_dialogs/javascript_dialog_views.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
+#include "ui/base/material_design/material_design_controller.h"
 
 JavaScriptDialog::JavaScriptDialog(content::WebContents* parent_web_contents) {
   dialog_helper_.reset(new AppModalDialogHelper(parent_web_contents));
@@ -27,7 +27,7 @@ base::WeakPtr<JavaScriptDialog> JavaScriptDialog::Create(
     const base::string16& default_prompt_text,
     const content::JavaScriptDialogManager::DialogClosedCallback&
         dialog_callback) {
-  if (chrome::ToolkitViewsWebUIDialogsEnabled()) {
+  if (ui::MaterialDesignController::IsSecondaryUiMaterial()) {
     return JavaScriptDialogViews::Create(
         parent_web_contents, alerting_web_contents, title, message_type,
         message_text, default_prompt_text, dialog_callback);