[cronet] Add mechanism for restarting CronetEnvironment

components/grpc_support/test/get_stream_engine.h

Index: components/grpc_support/test/get_stream_engine.h
diff --git a/components/grpc_support/test/get_stream_engine.h b/components/grpc_support/test/get_stream_engine.h
index 227733d4ab9ab107171ca3e9a69388da440230ef..90b4e531a3c2f4b22463789d442e35ab033df601 100644
--- a/components/grpc_support/test/get_stream_engine.h
+++ b/components/grpc_support/test/get_stream_engine.h
@@ -14,6 +14,18 @@ namespace grpc_support {
 // and should have kTestServerHost configured as a QUIC server.
 stream_engine* GetTestStreamEngine(int port);
 
+// Starts the stream_engine* for testing with the QuicTestServer.
+// Has the same properties as GetTestStreamEngine.  This function is
+// used when the stream_engine* needs to be shut down and restarted
+// between test cases (including between all of the bidirectional
+// stream test cases and all other tests for the engine; this is the
+// situation for Cronet).
+void StartTestStreamEngine(int port);
+
+// Shuts a stream_engine* started with |StartTestStreamEngine| down.
+// See comment above.
+void ShutdownTestStreamEngine();
+
 }  // namespace grpc_support
 
 #endif  // COMPONENTS_GRPC_SUPPORT_TEST_GET_REQUEST_CONTEXT_GETTER_H_