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

chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm

Index: chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm b/chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm
index 21c71222acbd9776214560973b71dea92ec569c9..4c3889961755a7f665bcbf7a78ecad9dd47ea591 100644
--- a/chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm
+++ b/chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.mm
@@ -12,11 +12,11 @@
 #include "chrome/browser/extensions/api/chrome_device_permissions_prompt.h"
 #include "chrome/browser/extensions/chrome_extension_chooser_dialog.h"
 #include "chrome/browser/extensions/device_permissions_dialog_controller.h"
-#include "chrome/browser/ui/browser_dialogs.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_window.h"
 #import "chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa_controller.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
+#include "ui/base/material_design/material_design_controller.h"
 
 ChooserDialogCocoa::ChooserDialogCocoa(
     content::WebContents* web_contents,
@@ -53,9 +53,10 @@ void ChooserDialogCocoa::Dismissed() {
 
 void ChromeExtensionChooserDialog::ShowDialog(
     std::unique_ptr<ChooserController> chooser_controller) const {
-  if (chrome::ToolkitViewsWebUIDialogsEnabled())
+  if (ui::MaterialDesignController::IsSecondaryUiMaterial()) {
     return ChromeExtensionChooserDialog::ShowDialogImpl(
         std::move(chooser_controller));
+  }
 
   web_modal::WebContentsModalDialogManager* manager =
       web_modal::WebContentsModalDialogManager::FromWebContents(web_contents_);
@@ -68,7 +69,7 @@ void ChromeExtensionChooserDialog::ShowDialog(
 }
 
 void ChromeDevicePermissionsPrompt::ShowDialog() {
-  if (chrome::ToolkitViewsWebUIDialogsEnabled())
+  if (ui::MaterialDesignController::IsSecondaryUiMaterial())
     return ChromeDevicePermissionsPrompt::ShowDialogViews();
 
   std::unique_ptr<ChooserController> chooser_controller(