Update 4f linear gradient selection heuristic

Use the 4f context when

  * dest type is 4f
  * there's no perpective

Keeping the define and testing flag overrides for now.

R=reed@google.com,herb@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1725793003

Review URL: https://codereview.chromium.org/1725793003
2 files changed