purge nss files and dependencies

BUG=webrtc:4497

Review URL: https://codereview.webrtc.org/1313233005

Cr-Original-Commit-Position: refs/heads/master@{#9862}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5647a2cf3db888195c928a1259d98f72f6ecbc15
16 files changed