added constant folding & branch elimination to skslc

src/sksl/SkSLIRGenerator.h

Index: src/sksl/SkSLIRGenerator.h
diff --git a/src/sksl/SkSLIRGenerator.h b/src/sksl/SkSLIRGenerator.h
index b0a449aceac23532d3f476aaefdfbea6a8a56d8a..d4a684638c213ca3885cca5eb4721b7ba317f218 100644
--- a/src/sksl/SkSLIRGenerator.h
+++ b/src/sksl/SkSLIRGenerator.h
@@ -164,6 +164,7 @@ private:
     std::unique_ptr<Statement> convertVarDeclarationStatement(const ASTVarDeclarationStatement& s);
     std::unique_ptr<Statement> convertWhile(const ASTWhileStatement& w);
 
+    void fixRectSampling(std::vector<std::unique_ptr<Expression>>& arguments);
     void checkValid(const Expression& expr);
     void markWrittenTo(const Expression& expr, bool readWrite);