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This updates run_cwt_chromedriver.py to account for changes
in xcodebuild_runner.

This also updates the default OS and device to more recent values.

Change-Id: I832419dc1d8247680a8324b09a047824fb56107e
Bug: 1158540
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2585816Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Ali Juma <ajuma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836849}