Revert "When clearing the priority message queue, don't copy an item to itself."

This reverts commit 2bffc3cb72e2250cbf6ed7e5f4b399395ca046cb.

BUG=4100
R=juberti@webrtc.org,pthatcher@webrtc.org
TBR=juberti@webrtc.org,pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/38189004

Cr-Original-Commit-Position: refs/heads/master@{#8450}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 2af3057b240526c9e769afc9147cfb532c07ad67
2 files changed