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

runtime/vm/il_printer.cc

Index: runtime/vm/il_printer.cc
===================================================================
--- runtime/vm/il_printer.cc	(revision 10207)
+++ runtime/vm/il_printer.cc	(working copy)
@@ -236,12 +236,12 @@
 
 
 void LoadLocalComp::PrintOperandsTo(BufferFormatter* f) const {
-  f->Print("%s lvl:%d", local().name().ToCString(), context_level());
+  f->Print("%s lvl:%d", local()->name().ToCString(), context_level());
 }
 
 
 void StoreLocalComp::PrintOperandsTo(BufferFormatter* f) const {
-  f->Print("%s, ", local().name().ToCString());
+  f->Print("%s, ", local()->name().ToCString());
   value()->PrintTo(f);
   f->Print(", lvl: %d", context_level());
 }
@@ -372,8 +372,8 @@
 
 void CatchEntryComp::PrintOperandsTo(BufferFormatter* f) const {
   f->Print("%s, %s",
-           exception_var().name().ToCString(),
-           stacktrace_var().name().ToCString());
+           exception_var()->name().ToCString(),
+           stacktrace_var()->name().ToCString());
 }