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

src/sksl/ir/SkSLSymbolTable.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSLSymbolTable.h"
 #include "SkSLUnresolvedFunction.h"
 
@@ skipping 79 matching lines @@
             functions.push_back((const FunctionDeclaration*) symbol);
             UnresolvedFunction* u = new UnresolvedFunction(std::move(functions));
             fSymbols[name] = u;
             this->takeOwnership(u);
         }
     } else {
         fErrorReporter.error(symbol->fPosition, "symbol '" + name + "' was already defined");
     }
 }
 
+
+void SymbolTable::markAllFunctionsBuiltin() {
+    for (const auto& pair : fSymbols) {
+        switch (pair.second->fKind) {
+            case Symbol::kFunctionDeclaration_Kind:
+                ((FunctionDeclaration&) *pair.second).fBuiltin = true;
+                break;
+            case Symbol::kUnresolvedFunction_Kind:
+                for (auto& f : ((UnresolvedFunction&) *pair.second).fFunctions) {
+                    ((FunctionDeclaration*) f)->fBuiltin = true;
+                }
+                break;
+            default:
+                break;
+        }
+    }
+}
+
 } // namespace