Support luminance-alpha GL format for YUVA planes

Bug: skia:10632
Change-Id: Ic91510b55644c15ee4eb5f96e7c35193b5ce49df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/344761
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/gl/GrGLUtil.cpp b/src/gpu/gl/GrGLUtil.cpp
index 3340ee9..73387ba 100644
--- a/src/gpu/gl/GrGLUtil.cpp
+++ b/src/gpu/gl/GrGLUtil.cpp
@@ -629,6 +629,7 @@
         case GrGLFormat::kR8:
         case GrGLFormat::kALPHA8:
         case GrGLFormat::kLUMINANCE8:
+        case GrGLFormat::kLUMINANCE8_ALPHA8:
         case GrGLFormat::kBGRA8:
         case GrGLFormat::kRGB565:
         case GrGLFormat::kRGBA16F: