[Chromoting] Add DataChannelManager to manage optional incoming data channels

remoting/protocol/BUILD.gn

Index: remoting/protocol/BUILD.gn
diff --git a/remoting/protocol/BUILD.gn b/remoting/protocol/BUILD.gn
index f9d4099c6b8bbad9111fa86557425222b9453928..9cbbd57a60bb3625fe854acd156d041e9b0ab3ae 100644
--- a/remoting/protocol/BUILD.gn
+++ b/remoting/protocol/BUILD.gn
@@ -49,6 +49,10 @@ static_library("protocol") {
     "content_description.cc",
     "content_description.h",
     "datagram_channel_factory.h",
+    "data_channel_handler.cc",
+    "data_channel_handler.h",
+    "data_channel_manager.cc",
+    "data_channel_manager.h",
     "errors.cc",
     "errors.h",
     "frame_consumer.h",
@@ -266,6 +270,10 @@ static_library("test_support") {
     "fake_connection_to_host.h",
     "fake_datagram_socket.cc",
     "fake_datagram_socket.h",
+    "fake_message_pipe.cc",
+    "fake_message_pipe.h",
+    "fake_message_pipe_wrapper.cc",
+    "fake_message_pipe_wrapper.h",
     "fake_session.cc",
     "fake_session.h",
     "fake_stream_socket.cc",
@@ -309,6 +317,7 @@ source_set("unit_tests") {
     "connection_tester.cc",
     "connection_tester.h",
     "content_description_unittest.cc",
+    "data_channel_manager_unittest.cc",
     "http_ice_config_request_unittest.cc",
     "ice_transport_unittest.cc",
     "input_event_tracker_unittest.cc",