Cronet: Use stale DNS cache entries experimentally.

net/dns/host_resolver.h

Index: net/dns/host_resolver.h
diff --git a/net/dns/host_resolver.h b/net/dns/host_resolver.h
index 5c371e43ad533e66ed0f366c36f5f17bb73e1bf7..8147a33c9935ef2ffcbb4f0bf577ec239c84b735 100644
--- a/net/dns/host_resolver.h
+++ b/net/dns/host_resolver.h
@@ -28,6 +28,7 @@ namespace net {
 
 class AddressList;
 class BoundNetLog;
+class HostResolverImpl;
 class HostResolverProc;
 class NetLog;
 
@@ -189,11 +190,16 @@ class NET_EXPORT HostResolver {
   // Creates a HostResolver implementation that queries the underlying system.
   // (Except if a unit-test has changed the global HostResolverProc using
   // ScopedHostResolverProc to intercept requests to the system).
+  static std::unique_ptr<HostResolverImpl> CreateSystemResolverImpl(
+      const Options& options,
+      NetLog* net_log);
   static std::unique_ptr<HostResolver> CreateSystemResolver(
       const Options& options,
       NetLog* net_log);
 
   // As above, but uses default parameters.
+  static std::unique_ptr<HostResolverImpl> CreateDefaultResolverImpl(
+      NetLog* net_log);
   static std::unique_ptr<HostResolver> CreateDefaultResolver(NetLog* net_log);
 
  protected: