Revert of Remove Client= from device/serial/data_stream.mojom.

device/serial/data_stream.mojom

Index: device/serial/data_stream.mojom
diff --git a/device/serial/data_stream.mojom b/device/serial/data_stream.mojom
index e54780677f9d4c25985b3aa7e860cd398c527585..a288eb26d568a8ffce4d42eb2726db277db0211a 100644
--- a/device/serial/data_stream.mojom
+++ b/device/serial/data_stream.mojom
@@ -4,6 +4,7 @@
 
 module device.serial;
 
+[Client=DataSourceClient]
 interface DataSource {
   // Initializes this DataSource with the amount of data its client will
   // buffer.
@@ -26,6 +27,7 @@
   OnData(array<uint8> data);
 };
 
+[Client=DataSinkClient]
 interface DataSink {
   // Initializes this DataSink with the amount of data it is expected to
   // buffer.