initial checkin of SkSL compiler

src/sksl/ir/SkSLVariableReference.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+ 
+#ifndef SKSL_VARIABLEREFERENCE
+#define SKSL_VARIABLEREFERENCE
+
+#include "SkSLExpression.h"
+
+namespace SkSL {
+
+/**
+ * A reference to a variable, through which it can be read or written. In the statement:
+ *
+ * x = x + 1;
+ *
+ * there is only one Variable 'x', but two VariableReferences to it.
+ */
+struct VariableReference : public Expression {
+    VariableReference(Position position, std::shared_ptr<Variable> variable)
+    : INHERITED(position, kVariableReference_Kind, variable->fType)
+    , fVariable(std::move(variable)) {}
+
+    std::string description() const override {
+        return fVariable->fName;
+    }
+
+    const std::shared_ptr<Variable> fVariable;
+
+    typedef Expression INHERITED;
+};
+
+} // namespace
+
+#endif