Revert of SkSL performance improvements

src/sksl/ir/SkSLField.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_FIELD
 #define SKSL_FIELD
 
 #include "SkSLModifiers.h"
 #include "SkSLPosition.h"
 #include "SkSLSymbol.h"
 #include "SkSLType.h"
 
 namespace SkSL {
 
 /** 
  * A symbol which should be interpreted as a field access. Fields are added to the symboltable 
  * whenever a bare reference to an identifier should refer to a struct field; in GLSL, this is the 
  * result of declaring anonymous interface blocks.
  */
 struct Field : public Symbol {
-    Field(Position position, const Variable& owner, int fieldIndex)
-    : INHERITED(position, kField_Kind, owner.fType.fields()[fieldIndex].fName)
+    Field(Position position, std::shared_ptr<Variable> owner, int fieldIndex)
+    : INHERITED(position, kField_Kind, owner->fType->fields()[fieldIndex].fName)
     , fOwner(owner)
     , fFieldIndex(fieldIndex) {}
 
     virtual std::string description() const override {
-        return fOwner.description() + "." + fOwner.fType.fields()[fFieldIndex].fName;
+        return fOwner->description() + "." + fOwner->fType->fields()[fFieldIndex].fName;
     }
 
-    const Variable& fOwner;
+    const std::shared_ptr<Variable> fOwner;
     const int fFieldIndex;
 
     typedef Symbol INHERITED;
 };
 
 } // namespace SkSL
 
 #endif