Remove blink::NetworkHintsInterface

Get rid of NetworkHintsInterface and replace it with
WebPrescientNetworking.
Mock classes which subclass NetworkHintsInterface for tests
also changed to subclass of WebPrescientNetworking.

Bug: 939636
Change-Id: I12aa8a2769262490377d20ea89a1ab0bfbd68a88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1513796
Commit-Queue: Hwanseung Lee <hs1217.lee@samsung.com>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642382}
21 files changed