Implement utility-side proxy resolver factory Mojo service.

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index d664409e9df20d71249c8ae964cd08f7943a6a43..1cb4bd715ea07f974e95735c09ff24b7b5fe7b0a 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -825,6 +825,8 @@ if (use_v8_in_net && !is_android) {
     sources = [
       "dns/host_resolver_mojo.cc",
       "dns/host_resolver_mojo.h",
+      "proxy/mojo_proxy_resolver_factory_impl.cc",
+      "proxy/mojo_proxy_resolver_factory_impl.h",
       "proxy/mojo_proxy_resolver_impl.cc",
       "proxy/mojo_proxy_resolver_impl.h",
     ]
@@ -1379,6 +1381,7 @@ if (!is_android && !is_win && !is_mac) {
       sources -= [
         "dns/host_resolver_mojo_unittest.cc",
         "dns/mojo_host_resolver_impl_unittest.cc",
+        "proxy/mojo_proxy_resolver_factory_impl_unittest.cc",
         "proxy/mojo_proxy_resolver_impl_unittest.cc",
       ]
     }