Expose API to detect when captive portal probe was blocked on Android

net/base/network_change_notifier.cc

Index: net/base/network_change_notifier.cc
diff --git a/net/base/network_change_notifier.cc b/net/base/network_change_notifier.cc
index 0cfaaa38d259db9be27343bf487aaf3b88d1a6a0..b98827559c8cdcf7e8642e144d5da7f9dda2147e 100644
--- a/net/base/network_change_notifier.cc
+++ b/net/base/network_change_notifier.cc
@@ -673,6 +673,13 @@ NetworkChangeNotifier::GetDefaultNetwork() {
 }
 
 // static
+bool NetworkChangeNotifier::GetNetworkCaptivePortal() {
+  return g_network_change_notifier
+             ? g_network_change_notifier->GetCurrentNetworkCaptivePortal()
+             : false;
+}
+
+// static
 void NetworkChangeNotifier::GetDnsConfig(DnsConfig* config) {
   if (!g_network_change_notifier) {
     *config = DnsConfig();
@@ -1018,6 +1025,10 @@ NetworkChangeNotifier::GetCurrentDefaultNetwork() const {
   return kInvalidNetworkHandle;
 }
 
+bool NetworkChangeNotifier::GetCurrentNetworkCaptivePortal() const {
+  return false;
+}
+
 // static
 void NetworkChangeNotifier::NotifyObserversOfIPAddressChange() {
   if (g_network_change_notifier &&