Enable the mojo-based serial API in the renderer behind a flag.

extensions/renderer/api/serial/data_sender_unittest.cc

Index: extensions/renderer/api/serial/data_sender_unittest.cc
diff --git a/extensions/renderer/api/serial/data_sender_unittest.cc b/extensions/renderer/api/serial/data_sender_unittest.cc
index 77dcfe169b8ee70a0c6f86dcaf355168b0333586..b042c07b262176618e265f7bbf3cbcf68e21574e 100644
--- a/extensions/renderer/api/serial/data_sender_unittest.cc
+++ b/extensions/renderer/api/serial/data_sender_unittest.cc
@@ -18,12 +18,6 @@ class DataSenderTest : public ApiTestBase {
 
   virtual void SetUp() override {
     ApiTestBase::SetUp();
-    env()->RegisterModule("async_waiter", IDR_ASYNC_WAITER_JS);
-    env()->RegisterModule("data_sender", IDR_DATA_SENDER_JS);
-    env()->RegisterModule("device/serial/data_stream.mojom",
-                          IDR_DATA_STREAM_MOJOM_JS);
-    env()->RegisterModule("device/serial/data_stream_serialization.mojom",
-                          IDR_DATA_STREAM_SERIALIZATION_MOJOM_JS);
     service_provider()->AddService(
         base::Bind(&DataSenderTest::CreateDataSink, base::Unretained(this)));
   }