Add stencil formats to all the backends.

Currently there is nothing using these formats, but this change just adds
them along with a quaries about their properties. They will be used in a
follow up change.

Bug: skia:10727
Change-Id: Iaaf13baf372799d47c65bd974fd204a32be57617
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/322622
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/gl/GrGLUtil.cpp b/src/gpu/gl/GrGLUtil.cpp
index 0c7f8df..3340ee9 100644
--- a/src/gpu/gl/GrGLUtil.cpp
+++ b/src/gpu/gl/GrGLUtil.cpp
@@ -643,6 +643,9 @@
         case GrGLFormat::kRG16:
         case GrGLFormat::kRGBA16:
         case GrGLFormat::kRG16F:
+        case GrGLFormat::kSTENCIL_INDEX8:
+        case GrGLFormat::kSTENCIL_INDEX16:
+        case GrGLFormat::kDEPTH24_STENCIL8:
         case GrGLFormat::kUnknown:
             return false;
     }