Get rid of SCHANNEL code.

BUG=webrtc:5045

Review URL: https://codereview.webrtc.org/1383253002

Cr-Original-Commit-Position: refs/heads/master@{#10199}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 172f009be2d6b897b1fce952f19a6c5dd842fc86
7 files changed