DM: remove unnecessary use of std::function

This draw_to_canvas() function doesn't need the power of std::function.

This skips a copy or two, which is nice, and seems to clear
up most of my MSAN problems.  Why?  I do not know.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1718633002

CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Debug-MSAN-Trybot

Review URL: https://codereview.chromium.org/1718633002
3 files changed