Add empty error callbacks to createOffer and createAnswer in various tests

Not providing error callbacks is deprecated in Chromium 49 and
will not be supported in Chromium 50.

BUG=chromium:558983
TEST=video_ChromeRTCHWEncodeUsed,video_WebRtcPeerConnectionWithCamera,video_WebRtcPerf

Change-Id: Ib9f6ff9c14830d6370b10f30416a023f4d408b11
Reviewed-on: https://chromium-review.googlesource.com/326945
Commit-Ready: Guido Urdaneta <guidou@chromium.org>
Tested-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Henrik Kjellander <kjellander@chromium.org>
Reviewed-by: Rohit Makasana <rohitbm@chromium.org>
3 files changed