Implement the host side of serial connection I/O on data pipe.

extensions/renderer/api/serial/serial_api_unittest.cc

Index: extensions/renderer/api/serial/serial_api_unittest.cc
diff --git a/extensions/renderer/api/serial/serial_api_unittest.cc b/extensions/renderer/api/serial/serial_api_unittest.cc
index 530ce2e93b0ed0383d1b78dabfefe3656b3ab167..76262761202510d3d6ae8e5b33c4f4f8d4aad263 100644
--- a/extensions/renderer/api/serial/serial_api_unittest.cc
+++ b/extensions/renderer/api/serial/serial_api_unittest.cc
@@ -308,6 +308,8 @@ class SerialApiTest : public ApiTestBase {
     ApiTestBase::SetUp();
     env()->RegisterModule("serial", IDR_SERIAL_CUSTOM_BINDINGS_JS);
     env()->RegisterModule("serial_service", IDR_SERIAL_SERVICE_JS);
+    env()->RegisterModule("device/serial/data_stream.mojom",
+                          IDR_DATA_STREAM_MOJOM_JS);
     env()->RegisterModule("device/serial/serial.mojom", IDR_SERIAL_MOJOM_JS);
     service_provider()->AddService<device::serial::SerialService>(base::Bind(
         &SerialApiTest::CreateSerialService, base::Unretained(this)));