Implement utility-side host resolver Mojo client.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 377f16e9a9b3c67f9008b542d568fd46acaa04be..d664409e9df20d71249c8ae964cd08f7943a6a43 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -660,6 +660,7 @@ source_set("test_support") {
     "test/embedded_test_server/http_request.h",
     "test/embedded_test_server/http_response.cc",
     "test/embedded_test_server/http_response.h",
+    "test/event_waiter.h",
     "test/net_test_suite.cc",
     "test/net_test_suite.h",
     "test/python_utils.cc",
@@ -822,6 +823,8 @@ if (use_v8_in_net && !is_android) {
 
   source_set("net_utility_services") {
     sources = [
+      "dns/host_resolver_mojo.cc",
+      "dns/host_resolver_mojo.h",
       "proxy/mojo_proxy_resolver_impl.cc",
       "proxy/mojo_proxy_resolver_impl.h",
     ]
@@ -1374,6 +1377,7 @@ if (!is_android && !is_win && !is_mac) {
       ]
     } else {
       sources -= [
+        "dns/host_resolver_mojo_unittest.cc",
         "dns/mojo_host_resolver_impl_unittest.cc",
         "proxy/mojo_proxy_resolver_impl_unittest.cc",
       ]