Add files needed for WebRTC to the snapshot.

The desktop/screen capture in WebRTC is implemented in a self contained
way in the chrome layer, and there is no point in copying it. We just need
to ensure we ship it in our snapshot.

Change-Id: Ia17b905317fb0c2b142c672a0c79d33e0ee01f68
Reviewed-by: Andras Becsi <andras.becsi@digia.com>