Remove unnecessary Create() factory function in Blink's core/animation

Many classes in blink have supported factory functions with legacy
uses of RefPtr/adoptRef. It can block to make to use MakeGarbageCollected.
Besides some classes have supported both a factory function and a public
constructor. They aren't necessary.

This CL removes unnecessary Foo::Create() in //third_party/blink/renderer/core/animation
and make their constructors public, then make the callers use
std::make_unique_ptr<Foo> instead of their Create() factory functions.

Bug: 939691
Change-Id: If216c4dd940af4622cac8a9b072de6e841db84ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1517494
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#640178}
25 files changed