Implement utility-side host resolver Mojo client.

net/dns/host_resolver_mojo.h

Index: net/dns/host_resolver_mojo.h
diff --git a/net/dns/host_resolver_mojo.h b/net/dns/host_resolver_mojo.h
new file mode 100644
index 0000000000000000000000000000000000000000..d250b969a927c7775d78ab22303900fafa510cf4
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+++ b/net/dns/host_resolver_mojo.h
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+// 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.
+
+#ifndef NET_DNS_HOST_RESOLVER_MOJO_H_
+#define NET_DNS_HOST_RESOLVER_MOJO_H_
+
+#include "base/callback.h"
+#include "base/threading/thread_checker.h"
+#include "net/dns/host_resolver.h"
+#include "net/interfaces/host_resolver_service.mojom.h"
+#include "third_party/mojo/src/mojo/public/cpp/bindings/error_handler.h"
+
+namespace net {
+class AddressList;
+class BoundNetLog;
+
+// A HostResolver implementation that delegates to an interfaces::HostResolver
+// mojo interface.
+class HostResolverMojo : public HostResolver, public mojo::ErrorHandler {
+ public:
+  HostResolverMojo(interfaces::HostResolverPtr resolver,
+                   const base::Closure& disconnect_callback);
+  ~HostResolverMojo() override;
+
+  // HostResolver overrides.
+  int Resolve(const RequestInfo& info,
+              RequestPriority priority,
+              AddressList* addresses,
+              const CompletionCallback& callback,
+              RequestHandle* request_handle,
+              const BoundNetLog& source_net_log) override;
+  int ResolveFromCache(const RequestInfo& info,
+                       AddressList* addresses,
+                       const BoundNetLog& source_net_log) override;
+  void CancelRequest(RequestHandle req) override;
+
+ private:
+  class Job;
+
+  // mojo::ErrorHandler override.
+  void OnConnectionError() override;
+
+  interfaces::HostResolverPtr resolver_;
+
+  const base::Closure disconnect_callback_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostResolverMojo);
+};
+
+}  // namespace net
+
+#endif  // NET_DNS_HOST_RESOLVER_MOJO_H_