Inline Array.shift() fast path instead of using a code stub.

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 20d722c40a2534f86bf86e9781b424358f5444f1..bda7938c2e968198709679586edfe09f86301365 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -319,16 +319,6 @@ 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 };