Optimize functions containing try-catch.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
===================================================================
--- runtime/vm/flow_graph_optimizer.h	(revision 22613)
+++ runtime/vm/flow_graph_optimizer.h	(working copy)
@@ -44,6 +44,8 @@
 
   void InferSmiRanges();
 
+  void AnalyzeTryCatch();
+
   // Remove environments from the instructions which do not deoptimize.
   void EliminateEnvironments();
 
@@ -345,6 +347,14 @@
   GrowableArray<MaterializeObjectInstr*> materializations_;
 };
 
+
+// Optimize spill stores inside try-blocks by identifying values that always
+// contain a single known constant at catch block entry.
+class TryCatchAnalyzer : public AllStatic {
+ public:
+  static void Optimize(FlowGraph* flow_graph);
+};
+
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_OPTIMIZER_H_