GitLab

Based on https://crrev.com/c/1317344 and https://crrev.com/c/1317348,
this CL moves blink/public/platform/referrer.mojom into
blink/public/mojom, as part of Onion Soup efforts.

BUG=789854

Change-Id: I6832ae85d849ff5395da0b37b1cc7bfa63e1152f
Reviewed-on: https://chromium-review.googlesource.com/c/1319346Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Leon Han <leon.han@intel.com>
Cr-Commit-Position: refs/heads/master@{#605627}