Add support for input attachments in SkSL spirv

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=5115

Change-Id: I3e03a465a10c9aff62491d0f6e71105d1b650dab
Reviewed-on: https://skia-review.googlesource.com/5115
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/sksl/SkSLCompiler.cpp b/src/sksl/SkSLCompiler.cpp
index 62e5fa7..003f154 100644
--- a/src/sksl/SkSLCompiler.cpp
+++ b/src/sksl/SkSLCompiler.cpp
@@ -113,6 +113,9 @@
     ADD_TYPE(Image2D);
     ADD_TYPE(IImage2D);
 
+    ADD_TYPE(SubpassInput);
+    ADD_TYPE(SubpassInputMS);
+
     ADD_TYPE(GSampler1D);
     ADD_TYPE(GSampler2D);
     ADD_TYPE(GSampler3D);