Tweaks for new Objective-C API.

BUG=

Review URL: https://codereview.webrtc.org/1696673003

Cr-Original-Commit-Position: refs/heads/master@{#11872}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a2f7798ec2fe29652bade4ba6b3f29c65328360e
22 files changed