[turbofan] Turn common Guard operator into simplified TypeGuard.

src/compiler/simplified-operator-reducer.h

Index: src/compiler/simplified-operator-reducer.h
diff --git a/src/compiler/simplified-operator-reducer.h b/src/compiler/simplified-operator-reducer.h
index 13301c2af5ce27dd6df55de25b9b33f398f3e7f4..70750a854c79f0ddaded80cd92615514213b7c47 100644
--- a/src/compiler/simplified-operator-reducer.h
+++ b/src/compiler/simplified-operator-reducer.h
@@ -30,6 +30,7 @@ class SimplifiedOperatorReducer final : public Reducer {
 
  private:
   Reduction ReduceReferenceEqual(Node* node);
+  Reduction ReduceTypeGuard(Node* node);
 
   Reduction Change(Node* node, const Operator* op, Node* a);
   Reduction ReplaceFloat64(double value);