[NetworkChangeNotifier] Return more specific network connection types (ethernet/wifi) on OSX

BUG=725485,112937

Review-Url: https://codereview.chromium.org/2896203003
Cr-Commit-Position: refs/heads/master@{#475940}
diff --git a/net/base/network_config_watcher_mac.cc b/net/base/network_config_watcher_mac.cc
index 24eaee90..bc46c12 100644
--- a/net/base/network_config_watcher_mac.cc
+++ b/net/base/network_config_watcher_mac.cc
@@ -67,10 +67,7 @@
 }
 
 void NetworkConfigWatcherMacThread::Init() {
-  // Disallow IO to make sure NetworkConfigWatcherMacThread's helper thread does
-  // not perform blocking operations.
-  base::ThreadRestrictions::SetIOAllowed(false);
-
+  base::ThreadRestrictions::SetIOAllowed(true);
   delegate_->Init();
 
   // TODO(willchan): Look to see if there's a better signal for when it's ok to