DNS: Add stubs for persisting data across restarts

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 7dafe36425f58ade4fcf70b34c3c72fad38cb062..e5eda72c13e8233bcc15bf22c8ce796eccf3c794 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -126,6 +126,13 @@ component("net") {
     "//crypto:platform",
   ]
 
+  if (!enable_built_in_dns) {
+    sources -= [
+      "dns/address_sorter_posix.cc",
+      "dns/address_sorter_posix.h",
+    ]
+  }
+
   if (!is_nacl) {
     sources += gypi_values.net_non_nacl_sources
 
@@ -151,14 +158,6 @@ component("net") {
       }
     }
 
-    if (!enable_built_in_dns) {
-      sources -= [
-        "dns/address_sorter_posix.cc",
-        "dns/address_sorter_posix.h",
-        "dns/dns_client.cc",
-      ]
-    }
-
     if (!use_openssl_certs) {
       sources -= [
         "base/crypto_module_openssl.cc",