Add fuzz testers to //net for some functions with simple parsing APIs.

net/proxy/parse_proxy_rules_fuzzer.cc

Index: net/proxy/parse_proxy_rules_fuzzer.cc
diff --git a/net/proxy/parse_proxy_rules_fuzzer.cc b/net/proxy/parse_proxy_rules_fuzzer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..daece9d656bf91d750b8a4f78d93ca49a6f72450
--- /dev/null
+++ b/net/proxy/parse_proxy_rules_fuzzer.cc
@@ -0,0 +1,13 @@
+// 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 "net/proxy/proxy_config.h"
+
+// Entry point for LibFuzzer.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  net::ProxyConfig::ProxyRules rules;
+  std::string input(data, data + size);
+  rules.ParseFromString(input);
+  return 0;
+}