Improve Array.shift() performance for small arrays.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 546595ad419ea53f3a6ab4889ab65debba98b6a9..6f3fc83789a00dd5ba3ffe1f8b0f5fb903019a41 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -305,6 +305,16 @@ void ElementsTransitionAndStoreStub::InitializeInterfaceDescriptor(
 }
 
 
+void ArrayShiftStub::InitializeInterfaceDescriptor(
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { rax };
+  descriptor->register_param_count_ = 1;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      Builtins::c_function_address(Builtins::c_ArrayShift);
+}
+
+
 void BinaryOpICStub::InitializeInterfaceDescriptor(
     CodeStubInterfaceDescriptor* descriptor) {
   static Register registers[] = { rdx, rax };