Array() in optimized code can create with wrong ElementsKind in corner cases.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index b8aed9634906d37d1242d9f557d7cfcc43c0373a..a5a38cc4b0424af887a274041f22edcf2615eacc 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4063,7 +4063,15 @@ void LCodeGen::DoCallNewArray(LCallNewArray* instr) {
   DCHECK(ToRegister(instr->result()).is(rax));
 
   __ Set(rax, instr->arity());
-  __ LoadRoot(rbx, Heap::kUndefinedValueRootIndex);
+  if (instr->arity() == 1) {
+    // We only need the allocation site for the case we have a length argument.
+    // The case may bail out to the runtime, which will determine the correct
+    // elements kind with the site.
+    __ Move(rbx, instr->hydrogen()->site());
+  } else {
+    __ LoadRoot(rbx, Heap::kUndefinedValueRootIndex);
+  }
+
   ElementsKind kind = instr->hydrogen()->elements_kind();
   AllocationSiteOverrideMode override_mode =
       (AllocationSite::GetMode(kind) == TRACK_ALLOCATION_SITE)