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Implements the payload tracker class which is responsible for relaying
progress updates in percent and maintaining status of incoming payloads.
Also ensures that connection is closed when a terminal status is reached.

Bug: 1085068
Change-Id: I329674a3e27784860955e25280024de678f49b5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362896Reviewed-by: Alex Chau <alexchau@chromium.org>
Commit-Queue: Himanshu Jaju <himanshujaju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800348}