[canvaskit] Add JS optimization for int color
[canvaskit] Add JS optimization for int color

Also confirm that Flutter Web and Canvas represent colors
as ints in the same way.

Change-Id: Ie8c2f9a48542510063c9bbc408a8047e0cc3969f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293840
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia