Delete unused file screencastid.h.

BUG=None

Review-Url: https://codereview.webrtc.org/2433913003
Cr-Original-Commit-Position: refs/heads/master@{#14757}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 74097fd3f587c750a0db5e143c028ecf13b6cd46
6 files changed