Add data pipe wrappers to be used to implement serial receive.

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
new file mode 100644
index 0000000000000000000000000000000000000000..423eb944a0b76a366feeb03cb4bc8a2384cd4cb8
--- /dev/null
+++ b/device/serial/data_stream.mojom
@@ -0,0 +1,17 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module device.serial {
+
+[Client=DataSourceClient]
+interface DataSource {
+  Init(handle<data_pipe_producer> producer_handle);
+  Resume();
+};
+
+interface DataSourceClient {
+  OnError(uint32 bytes_since_last_error, int32 error);
+};
+
+}