Delete some unused header files.

NOTRY=True # two of the androids bots are not cooperating
BUG=

Review-Url: https://codereview.webrtc.org/2057533002
Cr-Original-Commit-Position: refs/heads/master@{#13099}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 602844aa5e2c0685fb4fcb579f3f54b2a48a1c8b