Remove FetchContext::ModifyPriorityForExperiment

Introduce ResourceFetcherProperties::IsSubframeDeprioritizationEnabled
instead. Move the priority modification logic to ResourceFetcher.

We need to have a IsMainFrame branch in ResourceFetcher in order to
record histograms. Once it is deprecated we should move the logic into
ResourceFetcherProperties and rename the method to something like
ShouldDeprioritizeRequest.

Bug: 914739
Change-Id: I6627ee9fd2860a257d68f64879a1cc5875685350
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1570961
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652491}
15 files changed