Revert of Turned on SkSL->GLSL compiler

src/sksl/ast/SkSLASTDeclaration.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_ASTDECLARATION
 #define SKSL_ASTDECLARATION
 
 #include "SkSLASTPositionNode.h"
 
 namespace SkSL {
 
 /**
  * Abstract supertype of declarations such as variables and functions. 
  */
 struct ASTDeclaration : public ASTPositionNode {
     enum Kind {
         kVar_Kind,
         kFunction_Kind,
         kInterfaceBlock_Kind,
-        kExtension_Kind,
-        kPrecision_Kind,
-        kModifiers_Kind
+        kExtension_Kind
     };
 
     ASTDeclaration(Position position, Kind kind)
     : INHERITED(position)
     , fKind(kind) {}
 
     Kind fKind;
 
     typedef ASTPositionNode INHERITED;
 };
 
 } // namespace
 
 #endif