Add symbolic_constants_posix and its test

util/posix/symbolic_constants_posix.h

Index: util/posix/symbolic_constants_posix.h
diff --git a/util/posix/symbolic_constants_posix.h b/util/posix/symbolic_constants_posix.h
new file mode 100644
index 0000000000000000000000000000000000000000..4fb4a358aa58fb16cc6cee367f729f35fdc4a041
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+++ b/util/posix/symbolic_constants_posix.h
@@ -0,0 +1,48 @@
+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_POSIX_SYMBOLIC_CONSTANTS_POSIX_H_
+#define CRASHPAD_UTIL_POSIX_SYMBOLIC_CONSTANTS_POSIX_H_
+
+#include <string>
+
+#include "base/strings/string_piece.h"
+#include "util/misc/symbolic_constants_common.h"
+
+namespace crashpad {
+
+//! \brief Converts a POSIX signal value to a textual representation.
+//!
+//! \param[in] signal The signal value to convert.
+//! \param[in] options Options affecting the conversion. ::kUseOr is ignored.
+//!     For ::kUnknownIsNumeric, the format is `"%d"`.
+//!
+//! \return The converted string.
+std::string SignalToString(int signal, SymbolicConstantToStringOptions options);
+
+//! \brief Converts a string to its corresponding POSIX signal value.
+//!
+//! \param[in] string The string to convert.
+//! \param[in] options Options affecting the conversion. ::kAllowOr is ignored.
+//! \param[out] signal The converted POSIX signal value.
+//!
+//! \return `true` on success, `false` if \a string could not be converted as
+//!     requested.
+bool StringToSignal(const base::StringPiece& string,
+                    StringToSymbolicConstantOptions options,
+                    int* signal);
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_POSIX_SYMBOLIC_CONSTANTS_POSIX_H_