[OnionSoup] Move worker_content_settings_proxy.mojom into blink/public/mojom/

This CL moves blink/public/web/worker_content_settings_proxy.mojom
into third_party/blink/public/mojom/worker/, in preparation for
onionsoupping some other mojom files using it.

BUG=789854

Change-Id: I366e3b98dd8f7327c7ac38c94fb3e24086cc0056
Reviewed-on: https://chromium-review.googlesource.com/c/1416560
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Leon Han <leon.han@intel.com>
Cr-Commit-Position: refs/heads/master@{#623616}
15 files changed