Use the latest hash with a commit position as webkit version
Use the latest hash with a commit position as webkit version

This will guarantee that a development build with a not yet commit HEAD
will also get a valid devtools frontend from the servers

BUG=535268
R=pfeldman@chromium.org,mnaganov@chromium.org,dpranke@chromium.org

Review URL: https://codereview.chromium.org/1361393002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#350565}

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