Delete deprecated PeerConnection methods, and corresponding using declarations.

BUG=None

Review-Url: https://codereview.webrtc.org/2632203003
Cr-Original-Commit-Position: refs/heads/master@{#17120}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7f067663acc38e6c2ca8502947c0a1353601f387
7 files changed