net: Add fuzzer for HostResolverImpl.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index a96fc8510ea19be7537225b2c9e138e7adb93a57..2d72e4bc34c4c43e04248189c9a267527fb21387 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -1696,6 +1696,8 @@ 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",
@@ -1873,6 +1875,21 @@ 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",