Reland of: Condition DRP and connection check from prefetcher

A previous CL added logic to enable link-rel: prefetch
when "PredictivePrefetchingAllowedOnAllConnectionTypes"
experiment is enabled (see change 1350210).

This CL applies the same logic for prefetches initiated by
external Android apps. This brings Android APIs in-par with
Chrome's logic.

The original CL for this got reverted. This is a reland.

Bug: 850609,914503
Change-Id: Ib26fb6be50fdc4a1fd8de9bc22c92d456141bbdb
TBR: alexilin@chromium.org,lizeb@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/1414292
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623519}
3 files changed