Fix up wacky_yuv_formats GM and GL caps

This CL:
  enables the Y416 row (i.e., uses RGBA_16161616)
  spruces up the GL caps configuration of R16, RG16, RGBA16 and RG16F

Change-Id: I405c5acaf3f31b7ab0e9797e6f5df1d4c41d70d0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/220535
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/gm/wacky_yuv_formats.cpp b/gm/wacky_yuv_formats.cpp
index 4e42246..a8cd873 100644
--- a/gm/wacky_yuv_formats.cpp
+++ b/gm/wacky_yuv_formats.cpp
@@ -999,12 +999,8 @@
         }
     }
 
-    // For this to work we need GrColorType::kRGBA_16 support, i.e.:
-    //    GL:  RGBA16 (required in GL 3.0, added by GL_EXT_texture_norm16 for ES3.1)
-    //    Vk:  VK_FORMAT_R16G16B16A16_UNORM
-    //    Mtl: MTLPixelFormatRGBA16Unorm
-//    *format = caps->getBackendFormatFromGrColorType(GrColorType::kRGBA_16161616,
-//                                                    GrSRGBEncoded::kNo);
+    *format = caps->getBackendFormatFromGrColorType(GrColorType::kRGBA_16161616,
+                                                    GrSRGBEncoded::kNo);
     return;
 }