Add a test for ArgumentsAccessStub::GenerateNewNonStrictSlow

src/a64/code-stubs-a64.cc

Index: src/a64/code-stubs-a64.cc
diff --git a/src/a64/code-stubs-a64.cc b/src/a64/code-stubs-a64.cc
index 959958e4c520344acd4ed7ed081be12e2bb3078f..2268492bbb300e1ff7553ceab986a994396499e9 100644
--- a/src/a64/code-stubs-a64.cc
+++ b/src/a64/code-stubs-a64.cc
@@ -3229,8 +3229,6 @@ void ArgumentsAccessStub::GenerateNewNonStrictSlow(MacroAssembler* masm) {
   //  jssp[8]:  address of receiver argument
   //  jssp[16]: function
 
-  ASM_UNIMPLEMENTED("GenerateNewNonStrictSlow: This has not been tested.");
-
   // Check if the calling frame is an arguments adaptor frame.
   Label runtime;
   Register caller_fp = x10;