[cronet] Add mechanism for restarting CronetEnvironment

components/grpc_support/test/get_stream_engine.cc

Index: components/grpc_support/test/get_stream_engine.cc
diff --git a/components/grpc_support/test/get_stream_engine.cc b/components/grpc_support/test/get_stream_engine.cc
index 8e6e429a8f723146edbe480cebe6bb0ec75db37b..e447f7d89dad5f48c0ba3547972d46df6a32a70b 100644
--- a/components/grpc_support/test/get_stream_engine.cc
+++ b/components/grpc_support/test/get_stream_engine.cc
@@ -126,4 +126,7 @@ stream_engine* GetTestStreamEngine(int port) {
   return &engine;
 }
 
+void StartTestStreamEngine(int port) {}
+void ShutdownTestStreamEngine() {}
+
 }  // namespace grpc_support