DEPS.xwalk: chromium-crosswalk roll f344a2f..a824a16

Include NET_WM_PID patch. Relevant pull request is
https://github.com/crosswalk-project/chromium-crosswalk/pull/105.

$ git log --oneline f344a2f..a824a16
a824a16 Merge pull request #105 from cmarcelo/net-wm-pid
984c4de [Views] Customize _NET_WM_PID for X11 window backing a Widget
Merge pull request #1468 from cmarcelo/update-deps-xwalk-net-wm-pid

Update DEPS.xwalk to include NET_WM_PID patch