Introduce ResourceFetcherProperties

This is a first step to cleanup FetchContext. This CL introduces
ResourceFetcherProperties for "global properties" mentioned in the
design doc[1] and move one property, IsMainFrame, to the interface.

1: https://docs.google.com/document/u/1/d/1nXH2uEZLp3UEcMFNKBMlNUcJmssrPhPWtM1d86j_HCM

Bug: 914739
Change-Id: I9829265b6a4bd41ff6b79db622c29bb4f21175de
Reviewed-on: https://chromium-review.googlesource.com/c/1388056
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621859}
28 files changed