OnionSoup: Move mojom files in public/platform to public/mojom

This CL moves unhandled_tap_notifier.mojom, site_engagement.mojom,
ukm.mojom and reporting.mojom in public/platform to public/mojom.

Bug: 919393
Change-Id: I430cc84b586bf989ed201cbe78f4b72fd2765cda
Reviewed-on: https://chromium-review.googlesource.com/c/1485694
Commit-Queue: Julie Jeongeun Kim <jkim@igalia.com>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636688}
30 files changed