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

runtime/vm/ast_printer.cc

Index: runtime/vm/ast_printer.cc
===================================================================
--- runtime/vm/ast_printer.cc	(revision 10207)
+++ runtime/vm/ast_printer.cc	(working copy)
@@ -55,16 +55,16 @@
 
 
 void AstPrinter::VisitGenericLocalNode(AstNode* node,
-                                       const LocalVariable& var) {
+                                       const LocalVariable* var) {
   OS::Print("(%s %s%s '%s'",
             node->Name(),
-            var.is_final() ? "final " : "",
-            String::Handle(var.type().Name()).ToCString(),
-            var.name().ToCString());
-  if (var.HasIndex()) {
-    OS::Print(" @%d", var.index());
-    if (var.is_captured()) {
-      OS::Print(" ctx %d", var.owner()->context_level());
+            var->is_final() ? "final " : "",
+            String::Handle(var->type().Name()).ToCString(),
+            var->name().ToCString());
+  if (var->HasIndex()) {
+    OS::Print(" @%d", var->index());
+    if (var->is_captured()) {
+      OS::Print(" ctx %d", var->owner()->context_level());
     }
   }
   node->VisitChildren(this);