net: Add fuzzer for HostResolverImpl.

net/dns/fuzzed_host_resolver.h

Index: net/dns/fuzzed_host_resolver.h
diff --git a/net/dns/fuzzed_host_resolver.h b/net/dns/fuzzed_host_resolver.h
new file mode 100644
index 0000000000000000000000000000000000000000..5ce13cb58bbeacad036ee8a7d481703cf4cacaa1
--- /dev/null
+++ b/net/dns/fuzzed_host_resolver.h
@@ -0,0 +1,79 @@
+// 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.
+
+#ifndef NET_DNS_FUZZED_HOST_RESOLVER_
+#define NET_DNS_FUZZED_HOST_RESOLVER_
+
+#include <stdint.h>
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/address_family.h"
+#include "net/dns/host_resolver.h"
+#include "net/dns/host_resolver_impl.h"
+#include "net/socket/fuzzed_socket_factory.h"
+
+namespace net {
+
+class AddressList;
+class ClientSocketFactory;
+class DnsClient;
+class NetLog;
+class ScopedDefaultHostResolverProc;
+
+// HostResolver that uses a fuzzer to determine what results to return. It
+// inherits from HostResolverImpl, unlike MockHostResolver, so more closely
+// matches real behavior.
+//
+// By default uses a mocked out system resolver, though can be configured to
+// use the built-in async resolver (Built in DNS stub resolver) with a fuzzed
+// set of UDP/TCP sockets.
+//
+// To make behavior most deterministic, does not use the WorkerPool to run its
+// simulated platform host resolver calls, instead runs them on the thread it is
+// created on.
+//
+// Note that it does not attempt to sort the resulting AddressList when using
+// the mock system resolver path.
+//
+// The async DNS client can make system calls in AddressSorterPosix, but other
+// methods that make system calls are stubbed out.
+class FuzzedHostResolver : public HostResolverImpl {
+ public:
+  // |data_provider| and |net_log| must outlive the FuzzedHostResolver.
+  FuzzedHostResolver(const Options& options,
+                     NetLog* net_log,
+                     FuzzedDataProvider* data_provider);
+  ~FuzzedHostResolver() override;
+
+  // Enable / disable the async resolver. When enabled, installs a
+  // DnsClient with fuzzed UDP and TCP sockets. Overrides
+  // HostResolverImpl method of the same name.
+  void SetDnsClientEnabled(bool enabled) override;
+
+ private:
+  // HostResolverImpl implementation:
+  bool IsIPv6Reachable(const BoundNetLog& net_log) override;
+  void RunLoopbackProbeJob() override;
+
+  FuzzedDataProvider* data_provider_;
+
+  // Used for UDP and TCP sockets if the async resolver is enabled.
+  FuzzedSocketFactory socket_factory_;
+
+  // Fixed value to be returned by IsIPv6Reachable.
+  const bool is_ipv6_reachable_;
+
+  NetLog* net_log_;
+
+  base::WeakPtrFactory<FuzzedDataProvider> data_provider_weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(FuzzedHostResolver);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_FUZZED_HOST_RESOLVER_