Use modern base APIs to avoid base::MessageLoop::current() calls in first_run_dialog.cc

This is one more identical change as https://chromium-review.googlesource.com/c/chromium/src/+/986535
in chrome/browser/ui/views which I'd missed in that CL.

TBR=sky@chromium.org

Bug: 825327
Change-Id: I6e3c8a1dbf0028c842fce9db1e4e1d4e648974f2
Reviewed-on: https://chromium-review.googlesource.com/996152Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548123}

chrome/browser/ui/views/first_run_dialog.cc

@@ -7,7 +7,6 @@
 #include <string>
 
 #include "base/bind.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "chrome/browser/first_run/first_run.h"
 #include "chrome/browser/metrics/metrics_reporting_state.h"
@@ -59,9 +58,7 @@ void FirstRunDialog::Show(Profile* profile) {
   FirstRunDialog* dialog = new FirstRunDialog(profile);
   views::DialogDelegate::CreateDialogWidget(dialog, NULL, NULL)->Show();
 
-  base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
-  base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
-  base::RunLoop run_loop;
+  base::RunLoop run_loop(base::RunLoop::Type::kNestableTasksAllowed);
   dialog->quit_runloop_ = run_loop.QuitClosure();
   run_loop.Run();
 }