GitLab

Converts PaintWorkletGlobalScope.registerPaint's second argument
|paintCtor| into IDL callback function type.  Also, makes
Paint Worklet use |PaintCallback| of callback function type.

Change-Id: I6706499705a116c85f5c092a46309854db88708c
Reviewed-on: https://chromium-review.googlesource.com/c/1478850Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634582}