Replace DialogScope with UnresponsiveSuppressor

The latter is global-wide.

atom/browser/unresponsive_suppressor.cc

@@ -0,0 +1,27 @@
+// Copyright (c) 2016 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "atom/browser/unresponsive_suppressor.h"
+
+namespace atom {
+
+namespace {
+
+int g_suppress_level = 0;
+
+}  // namespace
+
+bool IsUnresponsiveEventSuppressed() {
+  return g_suppress_level > 0;
+}
+
+UnresponsiveSuppressor::UnresponsiveSuppressor() {
+  g_suppress_level++;
+}
+
+UnresponsiveSuppressor::~UnresponsiveSuppressor() {
+  g_suppress_level--;
+}
+
+}  // namespace atom