Store pointer instead of reference to LocalVariable in ast and flow graph.

runtime/vm/flow_graph_builder.h

Index: runtime/vm/flow_graph_builder.h
===================================================================
--- runtime/vm/flow_graph_builder.h	(revision 10207)
+++ runtime/vm/flow_graph_builder.h	(working copy)
@@ -147,8 +147,8 @@
   PushArgumentInstr* PushArgument(Value* value);
 
  protected:
-  Computation* BuildStoreLocal(const LocalVariable& local, Value* value);
-  Computation* BuildLoadLocal(const LocalVariable& local);
+  Computation* BuildStoreLocal(const LocalVariable* local, Value* value);
+  Computation* BuildLoadLocal(const LocalVariable* local);
 
   // Helpers for translating parts of the AST.
   void TranslateArgumentList(const ArgumentListNode& node,
@@ -217,8 +217,8 @@
   void BuildConstructorCall(ConstructorCallNode* node,
                             PushArgumentInstr* alloc_value);
 
-  void BuildStoreContext(const LocalVariable& variable);
-  void BuildLoadContext(const LocalVariable& variable);
+  void BuildStoreContext(const LocalVariable* variable);
+  void BuildLoadContext(const LocalVariable* variable);
 
   void BuildThrowNode(ThrowNode* node);