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

net/base/registry_controlled_domains/get_domain_and_registry_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 "base/at_exit.h"
+#include "base/i18n/icu_util.h"
+#include "base/strings/string_piece.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+#include "url/gurl.h"
+
+// Initialize ICU.
+struct InitICU {
+  InitICU() { CHECK(base::i18n::InitializeICU()); }
+  base::AtExitManager at_exit_manager;
+};
+
+InitICU* init_icu = new InitICU();
+
+// Entry point for LibFuzzer.
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  net::registry_controlled_domains::PrivateRegistryFilter filter =
+      net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES;
+
+  // Consume the first byte to determine which filter mode to use.
+  if (size > 0) {
+    uint8_t first_byte = *data;
+    size--;

[mmoroz, 2016/02/26 09:18:45]

Since we use first byte of |data| and decrease |size|, it may be a good idea to
increase |data| pointer too.

However, if we need only 1 bit here, we also can do something like:
if (size > 1) {
  if ((data[0] ^ data[size - 1]) & 1)
    filter = ...; 
}

Formally speaking, that leaves some 'dependency' between |filter| and |data|
buffer passed to a target function, but we are ok with this.

[eroman, 2016/02/26 20:37:19]

Oops yes, that was my intent :)
Done.

+    if ((first_byte % 2) == 1)
+      filter = net::registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES;
+  }
+
+  std::string input(data, data + size);

[mmoroz, 2016/02/26 09:18:45]

Unused variable |input|?

[eroman, 2016/02/26 20:37:19]

Fixed.

+
+  net::registry_controlled_domains::GetDomainAndRegistry(
+      base::StringPiece(reinterpret_cast<const char*>(data), size), filter);
+
+  return 0;
+}