GitLab

This change adds DataSource and DataSink interface request parameters to
SerialService::Connect, passes them through to SerialConnection
instances via SerialConnectionFactory; the SerialConnection now uses a
DataSourceSender and a DataSinkReceiver for implementing serial receive
and send, respectively.

BUG=389016

Review URL: https://codereview.chromium.org/488363002

Cr-Commit-Position: refs/heads/master@{#292104}