Turned on SkSL->GLSL 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 "SkSLContext.h"
 #include "SkSLErrorReporter.h"
 #include "SkSLGLSLCodeGenerator.h"
 
+#define SK_FRAGCOLOR_BUILTIN 10001
+
 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.
+ *
+ * See the README for information about SkSL.
  */
 class Compiler : public ErrorReporter {
 public:
     Compiler();
 
     ~Compiler();
 
     std::unique_ptr<Program> convertProgram(Program::Kind kind, std::string text);
 
     bool toSPIRV(Program::Kind kind, const std::string& text, std::ostream& out);
     
     bool toSPIRV(Program::Kind kind, const std::string& text, std::string* out);
 
     bool toGLSL(Program::Kind kind, const std::string& text, GLCaps caps, std::ostream& out);
     
     bool toGLSL(Program::Kind kind, const std::string& text, GLCaps caps, std::string* out);
 
     void error(Position position, std::string msg) override;
 
     std::string errorText();
 
     void writeErrorCount();
 
 private:
 
     void internalConvertProgram(std::string text,
+                                Modifiers::Flag* defaultPrecision,
                                 std::vector<std::unique_ptr<ProgramElement>>* result);
 
     std::shared_ptr<SymbolTable> fTypes;
     IRGenerator* fIRGenerator;
     std::string fSkiaVertText; // FIXME store parsed version instead
 
     Context fContext;
     int fErrorCount;
     std::string fErrorText;
 };
 
 } // namespace
 
 #endif