Improve representation inference for HUnknownOSRValue.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 051b4ee6edbe04f1a48e9131056960de47f69ff4..fb5879fd90c15cedcbe0ed45dee448ec5d420af7 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -3423,13 +3423,27 @@ class HCallStub: public HUnaryCall {
 
 class HUnknownOSRValue: public HTemplateInstruction<0> {
  public:
-  HUnknownOSRValue() { set_representation(Representation::Tagged()); }
+  HUnknownOSRValue()
+      : incoming_value_(NULL) {
+    set_representation(Representation::Tagged());
+  }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::None();
   }
 
+  void set_incoming_value(HPhi* value) {
+    incoming_value_ = value;
+  }
+
+  HPhi* incoming_value() {
+    return incoming_value_;
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(UnknownOSRValue)
+
+ private:
+  HPhi* incoming_value_;
 };