re-re-land of skslc now automatically turns on derivatives support

src/sksl/ir/SkSLSymbolTable.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_SYMBOLTABLE
 #define SKSL_SYMBOLTABLE
 
@@ skipping 21 matching lines @@
     , fErrorReporter(errorReporter) {}
 
     const Symbol* operator[](const std::string& name);
 
     void add(const std::string& name, std::unique_ptr<Symbol> symbol);
 
     void addWithoutOwnership(const std::string& name, const Symbol* symbol);
 
     Symbol* takeOwnership(Symbol* s);
 
+    void markAllFunctionsBuiltin();
+
     const std::shared_ptr<SymbolTable> fParent;
 
 private:
     static std::vector<const FunctionDeclaration*> GetFunctions(const Symbol& s);
 
     std::vector<std::unique_ptr<Symbol>> fOwnedPointers;
 
     std::unordered_map<std::string, const Symbol*> fSymbols;
 
     ErrorReporter& fErrorReporter;
 };
 
 } // namespace
 
 #endif