Pretend all stand-alone WebView channels are stable for variations

Previously, stand-alone WebView had channel "unknown", meaning only
experiments with no channel filter would apply to it.

BUG=678288

Change-Id: I409703dcd170ca247619b11edc78fcbc8953aa75
Reviewed-on: https://chromium-review.googlesource.com/1149263
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578016}
1 file changed