Remove MockImageResourceObserver::Create() in core/loader

As advised in [1], this CL removes unnecessary InterpolateLists::Create()
in //third_party/blink/renderer/core/animation and make their constructors
public, then make the callers use std::make_unique<InterpolateLists>
instead of it's Create() factory function.

[1] https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/iJ1bawbxbWs/vEdfT5QtBgAJ

Bug: 939691
Change-Id: Ic507605e51ce825717f8663bebd735b72fa2b4f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1531893
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#642462}
2 files changed