Add gray_8_as_lum and _as_red private grpixelconfigs

Bug: skia:
Change-Id: I70cbd0bc9f7a7a16fb9f0688d272d7afa607700a
Reviewed-on: https://skia-review.googlesource.com/80622
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/vk/GrVkUtil.cpp b/src/gpu/vk/GrVkUtil.cpp
index 2f4e9b1..1b20605 100644
--- a/src/gpu/vk/GrVkUtil.cpp
+++ b/src/gpu/vk/GrVkUtil.cpp
@@ -49,8 +49,11 @@
         case kAlpha_8_as_Alpha_GrPixelConfig:
             return false;
         case kGray_8_GrPixelConfig:
+        case kGray_8_as_Red_GrPixelConfig:
             *format = VK_FORMAT_R8_UNORM;
             return true;
+        case kGray_8_as_Lum_GrPixelConfig:
+            return false;
         case kRGBA_float_GrPixelConfig:
             *format = VK_FORMAT_R32G32B32A32_SFLOAT;
             return true;