Linux: Monitor resolv.conf for changes and use that to reload resolver.

net/base/host_resolver_impl.h

Index: net/base/host_resolver_impl.h
diff --git a/net/base/host_resolver_impl.h b/net/base/host_resolver_impl.h
index 30772dfb5dfc15e1f99b8618d2b05b80b9d156fe..4c4581efa0f6b4b7d97b23166465319e7f25b5f2 100644
--- a/net/base/host_resolver_impl.h
+++ b/net/base/host_resolver_impl.h
@@ -62,7 +62,8 @@ namespace net {
 class NET_EXPORT HostResolverImpl
     : public HostResolver,
       NON_EXPORTED_BASE(public base::NonThreadSafe),
-      public NetworkChangeNotifier::IPAddressObserver {
+      public NetworkChangeNotifier::IPAddressObserver,
+      public NetworkChangeNotifier::DNSObserver {
  public:
   // The index into |job_pools_| for the various job pools. Pools with a higher
   // index have lower priority.
@@ -304,6 +305,9 @@ class NET_EXPORT HostResolverImpl
     retry_factor_ = retry_factor;
   }
 
+  // NetworkChangeNotifier::OnDNSChanged methods:
+  virtual void OnDNSChanged();
+
   // Cache of host resolution results.
   scoped_ptr<HostCache> cache_;