Delete empty API files and cleaned up includes.

TBR=glaznev@webrtc.org

BUG=webrtc:5426

Review URL: https://codereview.webrtc.org/1809053002

Cr-Original-Commit-Position: refs/heads/master@{#12039}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c9022f508644dc33c01b05cb22ebfc2be145d6b2
3 files changed