Made SkSL DSL into public API

In addition to the unsurprising changes to eliminate references to
src/, we also had to tighten up some C++17-isms as they are not
permitted in public headers.

Change-Id: Ie5005a33d7a135e69fb66beca5e7a5f960dbd453
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/378496
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/sksl/SkSLInliner.cpp b/src/sksl/SkSLInliner.cpp
index d0a4dd7..4c16b93 100644
--- a/src/sksl/SkSLInliner.cpp
+++ b/src/sksl/SkSLInliner.cpp
@@ -11,6 +11,7 @@
 #include <memory>
 #include <unordered_set>
 
+#include "include/private/SkSLLayout.h"
 #include "src/sksl/SkSLAnalysis.h"
 #include "src/sksl/ir/SkSLBinaryExpression.h"
 #include "src/sksl/ir/SkSLBoolLiteral.h"
@@ -36,7 +37,6 @@
 #include "src/sksl/ir/SkSLInlineMarker.h"
 #include "src/sksl/ir/SkSLIntLiteral.h"
 #include "src/sksl/ir/SkSLInterfaceBlock.h"
-#include "src/sksl/ir/SkSLLayout.h"
 #include "src/sksl/ir/SkSLNop.h"
 #include "src/sksl/ir/SkSLPostfixExpression.h"
 #include "src/sksl/ir/SkSLPrefixExpression.h"