Rename SkGifCodec, SkIcoCodec, SkWbmpCodec

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1567863003

Review URL: https://codereview.chromium.org/1567863003
8 files changed