Revert "Split EventWrapper in twain."

This reverts commit 9509fbfc301dd5412804ce5731afedc81480f2f8.

This is to debug a Chromium issue that WebRTC hangs if there is > 1 PeerConnection active in the browser on Win XP.

BUG=

TBR=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43019004

Cr-Commit-Position: refs/heads/master@{#8912}
25 files changed