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

extensions/renderer/api/serial/data_receiver_unittest.cc

Index: extensions/renderer/api/serial/data_receiver_unittest.cc
diff --git a/extensions/renderer/api/serial/data_receiver_unittest.cc b/extensions/renderer/api/serial/data_receiver_unittest.cc
index 2415e00568e465e996ac402bb66135e940114c4b..363115ae0f31f423a06a020912eb14209f76dff7 100644
--- a/extensions/renderer/api/serial/data_receiver_unittest.cc
+++ b/extensions/renderer/api/serial/data_receiver_unittest.cc
@@ -18,12 +18,6 @@ class DataReceiverTest : public ApiTestBase {
 
   virtual void SetUp() override {
     ApiTestBase::SetUp();
-    env()->RegisterModule("async_waiter", IDR_ASYNC_WAITER_JS);
-    env()->RegisterModule("data_receiver", IDR_DATA_RECEIVER_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(
         &DataReceiverTest::CreateDataSource, base::Unretained(this)));
   }