Add functions for setting an environment and rebinding a use.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
diff --git a/runtime/vm/flow_graph_optimizer.h b/runtime/vm/flow_graph_optimizer.h
index 5a13707787f21dcc179eabc04b38adf30b5601b6..83515bc50105d19292b921e70f2119e2c59e790e 100644
--- a/runtime/vm/flow_graph_optimizer.h
+++ b/runtime/vm/flow_graph_optimizer.h
@@ -162,19 +162,25 @@ class ParsedFunction;
 
 
 // Loop invariant code motion.
-class LICM : public AllStatic {
+class LICM : public ValueObject {
  public:
-  static void Optimize(FlowGraph* flow_graph);
+  explicit LICM(FlowGraph* flow_graph);
+
+  void Optimize();
 
  private:
-  static void Hoist(ForwardInstructionIterator* it,
-                    BlockEntryInstr* pre_header,
-                    Instruction* current);
-
-  static void TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
-                                         BlockEntryInstr* header,
-                                         BlockEntryInstr* pre_header,
-                                         CheckSmiInstr* current);
+  FlowGraph* flow_graph() const { return flow_graph_; }
+
+  void Hoist(ForwardInstructionIterator* it,
+             BlockEntryInstr* pre_header,
+             Instruction* current);
+
+  void TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
+                                  BlockEntryInstr* header,
+                                  BlockEntryInstr* pre_header,
+                                  CheckSmiInstr* current);
+
+  FlowGraph* const flow_graph_;
 };