[Zucchini] Implement patch writing and reading.

EnsemblePatchWriter and EnsemblePatchReader (and related items) are utility
classes to read and write patches by interfacing with buffers of raw data.

Bug: 729154
Change-Id: I1cf6f804e01e960177f25c6c79ea8570a27b5531
Reviewed-on: https://chromium-review.googlesource.com/560936
Commit-Queue: Etienne Pierre-Doray <[email protected]>
Reviewed-by: Samuel Huang <[email protected]>
Cr-Commit-Position: refs/heads/master@{#492547}
10 files changed