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

1 files changed, 5 insertions, 4 deletions

diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 366d8f860e..7ccaf223fc 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -1043,17 +1043,18 @@ Error RasterSink::draw(const Src& src, SkBitmap* dst, SkWStream*, SkString*) con
 // passing the Sink draw() arguments, a size, and a function draws into an SkCanvas.
 // Several examples below.
 
+template <typename Fn>
 static Error draw_to_canvas(Sink* sink, SkBitmap* bitmap, SkWStream* stream, SkString* log,
-                            SkISize size, std::function<Error(SkCanvas*)> draw) {
+                            SkISize size, const Fn& draw) {
     class ProxySrc : public Src {
     public:
-        ProxySrc(SkISize size, std::function<Error(SkCanvas*)> draw) : fSize(size), fDraw(draw) {}
+        ProxySrc(SkISize size, const Fn& draw) : fSize(size), fDraw(draw) {}
         Error   draw(SkCanvas* canvas) const override { return fDraw(canvas); }
         Name                    name() const override { sk_throw(); return ""; } // Won't be called.
         SkISize                 size() const override { return fSize; }
     private:
-        SkISize                         fSize;
-        std::function<Error(SkCanvas*)> fDraw;
+        SkISize   fSize;
+        const Fn& fDraw;
     };
     return sink->draw(ProxySrc(size, draw), bitmap, stream, log);
 }