chromium: Update beta and dev to latest versions.

beta: 37.0.2062.94 -> 38.0.2125.24 (builds fine, tested)
dev:  38.0.2125.8  -> 39.0.2138.3  (builds fine, tested)

Introduces the new version 39 and finally separates stable/beta again.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>