If a filter does not affect transparent black, there's no
reason to allow the crop rect to expand beyond the optimal
size determined by onFilterNodeBounds(). So don't enlarge
the bounds unless the filter affects transparent black.
In order to determine which filters affect transparent
black, I've pulled the inverse of the canComputeFastBounds()
logic into a non-recursive, affectsTransparentBlack()
virtual, and left canComputeFastBounds() as a non-virtual,
recursive function that calls it.
BUG=599933
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1848953002TBR=reed@google.com
Review URL: https://codereview.chromium.org/1848953002
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