Remove dependency from blink/public to webrtc/p2p

As part of making blink/public's dependencies automatically
checked by gn, this is one dependency that was unintended and
unnecessary. Moving the dependency into platform/export makes
for a cleaner API.

Bug: 800764

Change-Id: I4e5f2095bddc4e51de08ed16db51c248884dfd5f
Reviewed-on: https://chromium-review.googlesource.com/c/1301468
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#603370}
2 files changed