Remove ALL usage of CriticalSectionWrapper.

Finally we are able to remove this class entirely, along with the last
vestiges of it's use. I've also removed some legacy files that were only
used for windows XP support.

BUG=webrtc:7035

Review-Url: https://codereview.webrtc.org/2790533002
Cr-Original-Commit-Position: refs/heads/master@{#17480}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ff046c74c50c98bcd79274c31c10a65327c31ef1
30 files changed