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

net/base/sniff_mime_type_fuzzer.cc

Index: net/base/sniff_mime_type_fuzzer.cc
diff --git a/net/base/sniff_mime_type_fuzzer.cc b/net/base/sniff_mime_type_fuzzer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..02fbc1540c7b55516c627f05fa4be0f151b06e87
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+++ b/net/base/sniff_mime_type_fuzzer.cc
@@ -0,0 +1,18 @@
+// 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 "net/base/mime_sniffer.h"
+#include "url/gurl.h"
+
+// Entry point for LibFuzzer.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  std::string result;
+  net::SniffMimeType(reinterpret_cast<const char*>(data), size,
+                     GURL("http://www.example-url.com/xyz"), "", &result);
+
+  return 0;
+}