subprocess2: cache the string-escape codec at load time.
subprocess2: cache the string-escape codec at load time.

This is a speculative fix for subprocess being unable to find
string-escape later in execution; the theory being that something
(unclear what) is interfering w/ codecs' lookup logic and that calling
lookup earlier would allow string-escape to be cached before any such
interference. See crbug.com/912292#c2 for more.

Bug: 912292
Change-Id: I0abdd394253c9a4984db7c6c81d044087edc68fd
Reviewed-on: https://chromium-review.googlesource.com/c/1363753
Reviewed-by: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>
Commit-Queue: John Budorick <17d38a2d68c6a07a3ab0ce4a2873c5acefbd3dbb@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools