Replace DialogScope with UnresponsiveSuppressor

The latter is global-wide.

atom/browser/unresponsive_suppressor.h

@@ -0,0 +1,25 @@
+// Copyright (c) 2016 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef ATOM_BROWSER_UNRESPONSIVE_SUPPRESSOR_H_
+#define ATOM_BROWSER_UNRESPONSIVE_SUPPRESSOR_H_
+
+#include "base/macros.h"
+
+namespace atom {
+
+bool IsUnresponsiveEventSuppressed();
+
+class UnresponsiveSuppressor {
+ public:
+  UnresponsiveSuppressor();
+  ~UnresponsiveSuppressor();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(UnresponsiveSuppressor);
+};
+
+}  // namespace atom
+
+#endif  // ATOM_BROWSER_UNRESPONSIVE_SUPPRESSOR_H_