DEPS.xwalk: Roll chromium-crosswalk (122cb0c -> 8edfc5b).

Cherry-pick CL from upstream to fix crash issue.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2475, XWALK-2523
Merge pull request #2445 from crosswalk-project/roll-deps-crosswalk-8

DEPS.xwalk: Roll chromium-crosswalk (122cb0c -> 8edfc5b).