Apply snake_case to css/*.json5
Apply snake_case to css/*.json5

This CL has no behavior changes.

Bug: 770603
Change-Id: I1224d6eaeecccfcffc3c205595b526f5be272671
Reviewed-on: https://chromium-review.googlesource.com/1230453
Reviewed-by: Kent Tamura <e0e84ce4a33dcc115f06c0609c8bb50720a44e41@chromium.org>
Commit-Queue: Amos Lim <2e8452d5b6d4d1e5a84d19ac312176b79f24ecfd@samsung.com>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#592258}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: e081d88b6f03f2760164b4a12601469f9c37c97d
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