Sync the browser test host resolver with the network process before a test runs.

content/public/test/test_host_resolver.h

Index: content/public/test/test_host_resolver.h
diff --git a/content/public/test/test_host_resolver.h b/content/public/test/test_host_resolver.h
new file mode 100644
index 0000000000000000000000000000000000000000..1278970f04d30d13d54b6971162ea20f00ffa872
--- /dev/null
+++ b/content/public/test/test_host_resolver.h
@@ -0,0 +1,39 @@
+// Copyright 2017 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 CONTENT_PUBLIC_TEST_TEST_HOST_RESOLVER_H_
+#define CONTENT_PUBLIC_TEST_TEST_HOST_RESOLVER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+
+namespace net {
+class HostResolverProc;
+class RuleBasedHostResolverProc;
+class ScopedDefaultHostResolverProc;
+}
+
+namespace content {
+class TestHostResolver {
+ public:
+  TestHostResolver();
+  ~TestHostResolver();
+
+  net::RuleBasedHostResolverProc* host_resolver() {
+    return rule_based_resolver_.get();
+  }
+
+ private:
+  // Host resolver used during tests.
+  scoped_refptr<net::HostResolverProc> local_resolver_;
+  scoped_refptr<net::RuleBasedHostResolverProc> rule_based_resolver_;
+  std::unique_ptr<net::ScopedDefaultHostResolverProc>
+      scoped_local_host_resolver_proc_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestHostResolver);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_TEST_TEST_HOST_RESOLVER_H_