chrome-sdk: Add --sdk-path support

You can specify either a local directory or a gs:// path to pull SDK
components from with --sdk-path.  This is used by the builders to run
chrome-sdk with artifacts that have not yet been uploaded.

BUG=chromium:265607
TEST=Remote trybots

Change-Id: Ib743eb1bdbd0b5c53d5ed02aab01c1f349c40de9
Reviewed-on: https://gerrit.chromium.org/gerrit/63687
Commit-Queue: Ryan Cui <rcui@chromium.org>
Reviewed-by: Ryan Cui <rcui@chromium.org>
Tested-by: Ryan Cui <rcui@chromium.org>
3 files changed