Remove unnecessary feature flag update.

The feature flags in StyleEngine were always reset from
StyleResolver::finishAppendAuthorStyleSheets right before we called
combineCSSFeatureFlags with the exact same feature set.

R=dstockwell@chromium.org
BUG=401359,567021

Review URL: https://codereview.chromium.org/1743183003

Cr-Commit-Position: refs/heads/master@{#378719}
3 files changed