The move constructor was calling the move assignment operator, which
used std::swap on the members.  However, `this` was not constructed, so
std::swap was operating on uninitialized values.  Caught by UBSAN.

Bug: chromium:1159444
Change-Id: I65f2f0affd1461f880c59780f31a368779411f24
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2599936Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Ian Elliott <ianelliott@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>