[chromedriver] Fix commit positions for M49 and M51 snapshots.
[chromedriver] Fix commit positions for M49 and M51 snapshots.

BUG=
TBR=stgao@chromium.org

Review-Url: https://codereview.chromium.org/1975413002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#393676}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk