GitLab

The only stats dictionary that was missing was 'data-channel'. For it to
be included data channels had to be created. Added CreateDataChannel to
webrtc_browsertest_base.h/cc and peerconnection.js. Unittest updated to
EXPECT that no expected stats are missing.

Original CL: https://codereview.chromium.org/2527273003/
Reason for revert: A whitelist filter was landed roughly at the same
time as the the original CL, causing expected stats to be blacklisted.
In this re-land, the whitelist is updated.

BUG=chromium:627816

Review-Url: https://codereview.chromium.org/2533223003
Cr-Commit-Position: refs/heads/master@{#434963}