Move ResourceRequestBlockedReason into its own header.

As suggested in
https://chromium-review.googlesource.com/c/chromium/src/+/1035091
since we'll need to add this to content/browser/DEPS and the
WebURLError class isnt' a good fit for this.

Bug: 838291
Change-Id: I95491371a70fa4d765328b25d89f0a69149cc071
Reviewed-on: https://chromium-review.googlesource.com/1060111
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558861}
5 files changed