[turbofan] Boost performance of Array.prototype.shift by 4x.

src/compiler/js-builtin-reducer.h

Index: src/compiler/js-builtin-reducer.h
diff --git a/src/compiler/js-builtin-reducer.h b/src/compiler/js-builtin-reducer.h
index e792ad3c3afeb7bcb7dffe54c6736412200ee4a7..736ece34e4f5db27b7cc794dd5d45280a3140821 100644
--- a/src/compiler/js-builtin-reducer.h
+++ b/src/compiler/js-builtin-reducer.h
@@ -58,6 +58,7 @@ class V8_EXPORT_PRIVATE JSBuiltinReducer final
   Reduction ReduceArrayIsArray(Node* node);
   Reduction ReduceArrayPop(Node* node);
   Reduction ReduceArrayPush(Node* node);
+  Reduction ReduceArrayShift(Node* node);
   Reduction ReduceDateNow(Node* node);
   Reduction ReduceDateGetTime(Node* node);
   Reduction ReduceGlobalIsFinite(Node* node);