Metal: Remove redundant CommandQueue::mMetalCmdBuffersTmp Instead of a member variable, instantiate the temporary at the use site. Bug: angleproject:6842 Change-Id: I64848bc937ce2945e6ac55adea8a6dffcaf9b00d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3347649 Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: John Cunningham <johncunningham@apple.com> Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>