[mobile]expose network change available/unavailable APIs (envoyproxy#…

…36616)

Commit Message: expose network change available/unavailable APIs
Additional Description:
Risk Level: low
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: mobile only

---------

Signed-off-by: Renjie Tang <renjietang@google.com>
Signed-off-by: Gustavo <grnmeira@gmail.com>

mobile/library/cc/engine.cc

@@ -31,5 +31,9 @@ void Engine::onDefaultNetworkChanged(NetworkType network) {
   engine_->onDefaultNetworkChanged(network);
 }
 
+void Engine::onDefaultNetworkUnavailable() { engine_->onDefaultNetworkUnavailable(); }
+
+void Engine::onDefaultNetworkAvailable() { engine_->onDefaultNetworkAvailable(); }
+
 } // namespace Platform
 } // namespace Envoy

mobile/library/cc/engine.h

@@ -22,6 +22,8 @@ class Engine : public std::enable_shared_from_this<Engine> {
   std::string dumpStats();
   StreamClientSharedPtr streamClient();
   void onDefaultNetworkChanged(NetworkType network);
+  void onDefaultNetworkUnavailable();
+  void onDefaultNetworkAvailable();
 
   envoy_status_t terminate();
   Envoy::InternalEngine* engine() { return engine_; }