Fixing problems with RTP extension ID conflict resolution

If the same extension URI is used for both audio and video (such as
abs-send-time), we should be able to re-use the same ID. A conflict
only exists if two different URIs are attempting to use the same ID.

Review URL: https://codereview.webrtc.org/1286273003

Cr-Commit-Position: refs/heads/master@{#9749}
2 files changed