Add ProcessArgumentsForPID() (process_util) and its test

util/posix/process_util.h

Index: util/posix/process_util.h
diff --git a/util/posix/process_util.h b/util/posix/process_util.h
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+// 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_PROCESS_UTIL_POSIX_H_
+#define CRASHPAD_UTIL_POSIX_PROCESS_UTIL_POSIX_H_
+
+#include <unistd.h>
+
+#include <string>
+#include <vector>
+
+namespace crashpad {
+
+//! \brief Obtains the arguments used to launch a process.
+//!
+//! \param[in] pid The process ID of the process to examine.
+//! \param[out] argv The process’ arguments as passed to its `main()` function
+//!     as the \a argv parameter, possibly modified by the process.
+//!
+//! \return `true` on success, with \a argv populated appropriately. Otherwise,
+//!     `false`.
+//!
+//! \note This function may spuriously return `false` when used to examine a
+//!     process that it is calling `exec()`. If examining such a process, call
+//!     this function in a retry loop with a small (100ns) delay to avoid an
+//!     erroneous assumption that \a pid is not running.
+bool ProcessArgumentsForPID(pid_t pid, std::vector<std::string>* argv);
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_POSIX_PROCESS_UTIL_POSIX_H_