initial checkin of SkSL compiler

src/sksl/SkSLCompiler.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_COMPILER
+#define SKSL_COMPILER
+
+#include <vector>
+#include "ir/SkSLProgram.h"
+#include "ir/SkSLSymbolTable.h"
+#include "SkSLErrorReporter.h"
+
+namespace SkSL {
+
+class IRGenerator;
+
+/**
+ * Main compiler entry point. This is a traditional compiler design which first parses the .sksl
+ * file into an abstract syntax tree (a tree of ASTNodes), then performs semantic analysis to 
+ * produce a Program (a tree of IRNodes), then feeds the Program into a CodeGenerator to produce
+ * compiled output.
+ */
+class Compiler : public ErrorReporter {
+public:
+    Compiler();
+
+    ~Compiler();
+
+    std::unique_ptr<Program> convertProgram(Program::Kind kind, std::string text);
+
+        bool toSPIRV(Program::Kind kind, std::string text, std::ostream& out);
+        
+        bool toSPIRV(Program::Kind kind, std::string text, std::string* out);
+
+    void error(Position position, std::string msg) override;
+
+    std::string errorText();
+
+    void writeErrorCount();
+
+private:
+
+    void internalConvertProgram(std::string text,
+                                                        std::vector<std::unique_ptr<ProgramElement>>* result);
+
+    std::shared_ptr<SymbolTable> fTypes;
+    IRGenerator* fIRGenerator;
+    std::string fSkiaVertText; // FIXME store parsed version instead
+
+    int fErrorCount;
+    std::string fErrorText;
+};
+
+} // namespace
+
+#endif