import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

security/sandbox/chromium/base/strings/nullable_string16.h

@@ -0,0 +1,46 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_STRINGS_NULLABLE_STRING16_H_
+#define BASE_STRINGS_NULLABLE_STRING16_H_
+
+#include <iosfwd>
+
+#include "base/base_export.h"
+#include "base/strings/string16.h"
+
+namespace base {
+
+// This class is a simple wrapper for string16 which also contains a null
+// state.  This should be used only where the difference between null and
+// empty is meaningful.
+class NullableString16 {
+ public:
+  NullableString16() : is_null_(true) { }
+  NullableString16(const string16& string, bool is_null)
+      : string_(string), is_null_(is_null) {
+  }
+
+  const string16& string() const { return string_; }
+  bool is_null() const { return is_null_; }
+
+ private:
+  string16 string_;
+  bool is_null_;
+};
+
+inline bool operator==(const NullableString16& a, const NullableString16& b) {
+  return a.is_null() == b.is_null() && a.string() == b.string();
+}
+
+inline bool operator!=(const NullableString16& a, const NullableString16& b) {
+  return !(a == b);
+}
+
+BASE_EXPORT std::ostream& operator<<(std::ostream& out,
+                                     const NullableString16& value);
+
+}  // namespace base
+
+#endif  // BASE_STRINGS_NULLABLE_STRING16_H_