Add simple libfuzzer based test.

This tests the verifier and the parser.

Tested: on Linux.
Bug: 27230459
Change-Id: I3417faba9385dc941199c57a08d8a50c2faec1aa

tests/fuzzer/flatbuffers_parser_fuzzer.cc

@@ -0,0 +1,16 @@
+// Copyright 2015 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 "flatbuffers/idl.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  flatbuffers::Parser parser;
+  // Guarantee 0-termination.
+  std::string s(reinterpret_cast<const char *>(data), size);
+  parser.Parse(s.c_str());
+  return 0;
+}