Add capability for SkColorXform to output half floats

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2147763002
CQ_INCLUDE_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot;master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review-Url: https://codereview.chromium.org/2147763002
diff --git a/dm/DMSrcSink.h b/dm/DMSrcSink.h
index 50a3b5a..b05fdb0 100644
--- a/dm/DMSrcSink.h
+++ b/dm/DMSrcSink.h
@@ -225,7 +225,7 @@
 #endif
     };
 
-    ColorCodecSrc(Path, Mode);
+    ColorCodecSrc(Path, Mode, SkColorType);
 
     Error draw(SkCanvas*) const override;
     SkISize size() const override;
@@ -234,6 +234,7 @@
 private:
     Path                    fPath;
     Mode                    fMode;
+    SkColorType             fColorType;
 };
 
 class SKPSrc : public Src {