Make SkSpecialSurfaces always use kUnknown for their pixel geometry

This now matches how the SkDevices were being created by the device proxy and prevents LCD text from being inadvertently applied.

BUG=602555

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1878143004

Review URL: https://codereview.chromium.org/1878143004
2 files changed