Add Ganesh support for RGBA_16161616 and RG_half (take 2)

TBR=egdaniel@google.com
Bug: skia:9171
Change-Id: I862c87ba4bd55381b347333cf9ca23cf5389dff6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/220816
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/SkGr.cpp b/src/gpu/SkGr.cpp
index 27a12a7..70a1898 100644
--- a/src/gpu/SkGr.cpp
+++ b/src/gpu/SkGr.cpp
@@ -296,9 +296,11 @@
         case kRGB_888X_GrPixelConfig:
         case kRG_88_GrPixelConfig:
         case kBGRA_8888_GrPixelConfig:
-        // Experimental (for P016 and P010)
         case kR_16_GrPixelConfig:
         case kRG_1616_GrPixelConfig:
+        // Experimental (for Y416 and mutant P016/P010)
+        case kRGBA_16161616_GrPixelConfig:
+        case kRG_half_GrPixelConfig:
             return 0;
         case kRGB_565_GrPixelConfig:
             return 1;