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

src/sksl/SkSLCompiler.cpp

Index: src/sksl/SkSLCompiler.cpp
diff --git a/src/sksl/SkSLCompiler.cpp b/src/sksl/SkSLCompiler.cpp
index d4fbc95d395d75a3ab0ee78e6a260314e5544c2a..5b502dce2fb2b5511527462cd478d662730d2a9a 100644
--- a/src/sksl/SkSLCompiler.cpp
+++ b/src/sksl/SkSLCompiler.cpp
@@ -19,6 +19,7 @@
 #include "ir/SkSLIntLiteral.h"
 #include "ir/SkSLModifiersDeclaration.h"
 #include "ir/SkSLSymbolTable.h"
+#include "ir/SkSLUnresolvedFunction.h"
 #include "ir/SkSLVarDeclarations.h"
 #include "SkMutex.h"
 
@@ -135,6 +136,7 @@ Compiler::Compiler()
     Modifiers::Flag ignored1;
     std::vector<std::unique_ptr<ProgramElement>> ignored2;
     this->internalConvertProgram(SKSL_INCLUDE, &ignored1, &ignored2);
+    fIRGenerator->fSymbolTable->markAllFunctionsBuiltin();
     ASSERT(!fErrorCount);
 }
 
@@ -393,10 +395,11 @@ std::unique_ptr<Program> Compiler::convertProgram(Program::Kind kind, std::strin
             this->internalConvertProgram(SKSL_FRAG_INCLUDE, &ignored, &elements);
             break;
     }
+    fIRGenerator->fSymbolTable->markAllFunctionsBuiltin();
     Modifiers::Flag defaultPrecision;
     this->internalConvertProgram(text, &defaultPrecision, &elements);
     auto result = std::unique_ptr<Program>(new Program(kind, defaultPrecision, std::move(elements), 
-                                                       fIRGenerator->fSymbolTable));;
+                                                       fIRGenerator->fSymbolTable));
     fIRGenerator->popSymbolTable();
     this->writeErrorCount();
     return result;