autoupdate_EndToEnd: Support legacy argument name.

The tree vs prod problem hits again, so this adds support for legacy
argument name ('source_image_uri') as fallback option.

Note that backward compatible API hacks can only be safely remove once
all release branches catch up with the corresponding control file
changes. Adding TODO comments accordingly.

BUG=b:24405484
TEST=None

Change-Id: I23bb7ad5351ca5c6fa76b39846ef39623e2d24f9
Reviewed-on: https://chromium-review.googlesource.com/303051
Reviewed-by: Simran Basi <sbasi@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
1 file changed