Add fuzzer for PRTime() from NSPR.

testing/libfuzzer/fuzzers/prtime_fuzzer.cc

+// Copyright 2016 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.
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <string>
+
+#include "base/third_party/nspr/prtime.h"
+
+PRTime parsed_time;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  if (size < 1)
+    return 0;
+
+  const uint8_t selector = data[0];
+
+  // Using std::string instead of a (potentially faster) fixed buffer to catch
+  // accesses beyond the end of the string.
+  std::string str(reinterpret_cast<const char*>(data+1), size - 1);
+  PR_ParseTimeString(str.c_str(), selector & 1, &parsed_time);
+
+  return 0;
+}