SkSL performance improvements

src/sksl/ir/SkSLVariableReference.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_VARIABLEREFERENCE
 #define SKSL_VARIABLEREFERENCE
 
 #include "SkSLExpression.h"
 
 namespace SkSL {
 
 /**
  * A reference to a variable, through which it can be read or written. In the statement:
  *
  * x = x + 1;
  *
  * there is only one Variable 'x', but two VariableReferences to it.
  */
 struct VariableReference : public Expression {
-    VariableReference(Position position, std::shared_ptr<Variable> variable)
-    : INHERITED(position, kVariableReference_Kind, variable->fType)
-    , fVariable(std::move(variable)) {}
+    VariableReference(Position position, const Variable& variable)
+    : INHERITED(position, kVariableReference_Kind, variable.fType)
+    , fVariable(variable) {}
 
     std::string description() const override {
-        return fVariable->fName;
+        return fVariable.fName;
     }
 
-    const std::shared_ptr<Variable> fVariable;
+    const Variable& fVariable;
 
     typedef Expression INHERITED;
 };
 
 } // namespace
 
 #endif