Allow F16 color type on direct raster canvases

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2416063002

Review-Url: https://codereview.chromium.org/2416063002
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index fc2e48a..bcda0f2 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -3332,6 +3332,7 @@
         case kAlpha_8_SkColorType:
         case kRGB_565_SkColorType:
         case kN32_SkColorType:
+        case kRGBA_F16_SkColorType:
             break;
         default:
             return false;