Add a transient image filter cache to SkImage::makeWithFilter & PDF

Added a bench for makeWithFilter (~23 ms -> ~6 ms median locally).

Also fixed indentation.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2360663002

Review-Url: https://codereview.chromium.org/2360663002
6 files changed