Currently, the chromium_revision field in the layout test results JSON is a full commit position, including ref and number, e.g. "refs/heads/master{#123}".

Since we always want the commit position number on the main chromium/src master branch, we can change that field to be just a number.

Related place in the code: https://cs.chromium.org/chromium/src/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/models/test_run_results.py?l=318

Updating this will require updating that location, as well as webkitpy/common/net/layout_test_results.py and any other code that uses this field, including the results viewer page.