initial checkin of SkSL compiler

src/sksl/SkSLCodeGenerator.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_CODEGENERATOR
+#define SKSL_CODEGENERATOR
+
+#include "ir/SkSLProgram.h"
+#include <vector>
+#include <iostream>
+
+namespace SkSL {
+
+/**
+ * Abstract superclass of all code generators, which take a Program as input and produce code as
+ * output.
+ */
+class CodeGenerator {
+public:
+        virtual ~CodeGenerator() {}
+        
+    virtual void generateCode(Program& program, std::ostream& out) = 0;
+};
+
+} // namespace
+
+#endif