tree c6c07943e40f109d1eba6b29f9db54b40d61fe34
parent 53173b964f6f43c89dbaba41875fcadd7077b2ea
author Gilad Arnold <garnold@chromium.org> 1359132085 -0800
committer ChromeBot <chrome-bot@google.com> 1369264220 -0700

AU: do not copy filesystem during full updates

The filesystem copying stage is redundant during full updates, where the
partition is being entirely overwritten regardless of its previous
content. It is also a very wasteful step, causing intensive I/O and
kernel buffer pressure, and known to (sometimes) cause jank and
otherwise have detrimental effects on our user experience.

This CL eliminates filesystem copying for full updates:

1) The decision is based on whether the Omaha response indicates that
   this is a full update.

2) To be safe, we also ensure that the payload manifest does not contain
   old partition hashes, which is indicative of a delta update.

Note that it is generally desirable to base the decision solely on #2
above (and ignore #1 altogether). However, this will require more
extensive re-engineering of the update flow, as filesystem copying
currently happens prior to the manifest being downloaded.

BUG=chromium:189855
TEST=Full and delta updates run correctly on x86-alex

Change-Id: Ic0dc6e32913cfb96019606624ec6b87c2e5b3ebb
Reviewed-on: https://gerrit.chromium.org/gerrit/43665
Commit-Queue: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>