Clean up handling of guarded fields in the flow graph builder.

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
===================================================================
--- runtime/vm/flow_graph.h	(revision 27696)
+++ runtime/vm/flow_graph.h	(working copy)
@@ -197,6 +197,13 @@
 
   bool IsCompiledForOsr() const { return graph_entry()->IsCompiledForOsr(); }
 
+  static void AddToGuardedFields(const Field* field,

[Kevin Millikin (Google), 2013/09/20 12:04:28]

I like reversing the arguments here, because it matches (target, source) that we
use in a lot of other places.

[Florian Schneider, 2013/09/20 12:13:50]

Done.

+                                 ZoneGrowableArray<const Field*>* array);
+
+  ZoneGrowableArray<const Field*>* guarded_fields() const {
+    return guarded_fields_;
+  }
+
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
@@ -269,6 +276,7 @@
 
   ZoneGrowableArray<BlockEntryInstr*>* loop_headers_;
   ZoneGrowableArray<BitVector*>* loop_invariant_loads_;
+  ZoneGrowableArray<const Field*>* guarded_fields_;
 };