Add the task module.

BUG=None
TEST=unit testings for the pipeline stage, pipeline workers, generation,
steering and task.

Change-Id: I38987a12d7a48ec027d42465300a7226c760ea9d
Reviewed-on: https://gerrit-int.chromium.org/41659
Reviewed-by: Simon Que <sque@google.com>
Commit-Queue: Yuheng Long <yuhenglong@google.com>
Tested-by: Yuheng Long <yuhenglong@google.com>
4 files changed