Revert of SkSL performance improvements

src/sksl/ir/SkSLVariableReference.h

Index: src/sksl/ir/SkSLVariableReference.h
diff --git a/src/sksl/ir/SkSLVariableReference.h b/src/sksl/ir/SkSLVariableReference.h
index b443da1f22869fb4393c9f121836730352ae0d22..8499511a1b531e88ce00c6e4ddadccb0fb82c7c6 100644
--- a/src/sksl/ir/SkSLVariableReference.h
+++ b/src/sksl/ir/SkSLVariableReference.h
@@ -20,15 +20,15 @@
  * there is only one Variable 'x', but two VariableReferences to it.
  */
 struct VariableReference : public Expression {
-    VariableReference(Position position, const Variable& variable)
-    : INHERITED(position, kVariableReference_Kind, variable.fType)
-    , fVariable(variable) {}
+    VariableReference(Position position, std::shared_ptr<Variable> variable)
+    : INHERITED(position, kVariableReference_Kind, variable->fType)
+    , fVariable(std::move(variable)) {}
 
     std::string description() const override {
-        return fVariable.fName;
+        return fVariable->fName;
     }
 
-    const Variable& fVariable;
+    const std::shared_ptr<Variable> fVariable;
 
     typedef Expression INHERITED;
 };