net: Add fuzzer for HostResolverImpl.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index b6ac60532329490267dc680e17b6ecc422ca1790..c5d3d6871cff9a11b2365d62a4803e38b05b1f58 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -1727,6 +1727,8 @@ source_set("net_fuzzer_test_support") {
     "socket/fuzzed_socket.h",
     "socket/fuzzed_socket_factory.cc",
     "socket/fuzzed_socket_factory.h",
+    "udp/fuzzed_datagram_client_socket.cc",
+    "udp/fuzzed_datagram_client_socket.h",
   ]
   deps = [
     "//base",
@@ -1904,6 +1906,21 @@ fuzzer_test("net_dns_hosts_parse_fuzzer") {
   ]
 }
 
+fuzzer_test("net_host_resolver_impl_fuzzer") {
+  sources = [
+    "dns/fuzzed_host_resolver.cc",
+    "dns/fuzzed_host_resolver.h",
+    "dns/host_resolver_impl_fuzzer.cc",
+  ]
+  deps = [
+    ":net_fuzzer_test_support",
+    ":test_support",
+    "//base",
+    "//net",
+  ]
+  dict = "data/dns/dns.dict"
+}
+
 fuzzer_test("net_http_stream_parser_fuzzer") {
   sources = [
     "http/http_stream_parser_fuzzer.cc",