Improve Array.shift() performance for small arrays.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 12f2ee0e5ce980e9009a80d944bb30a92a2b3828..f961a28d7abb48cd7601eb3bbd997351e9652c2f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -6810,6 +6810,7 @@ class Script: public Struct {
 #define FUNCTIONS_WITH_ID_LIST(V)                   \
   V(Array.prototype, push, ArrayPush)               \
   V(Array.prototype, pop, ArrayPop)                 \
+  V(Array.prototype, shift, ArrayShift)             \
   V(Function.prototype, apply, FunctionApply)       \
   V(String.prototype, charCodeAt, StringCharCodeAt) \
   V(String.prototype, charAt, StringCharAt)         \