[cleanup] Cleanup JSArray::AllowsSetLength

Looks like historical leftovers from the time when we had "pixel arrays"
and external array elements kinds. See
https://codereview.chromium.org/1262583002

Bug: v8:11111
Change-Id: I288d47ae802218737bd6226cbb999c3289d1dbaf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3574548Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79823}

src/objects/js-array-inl.h

@@ -43,12 +43,6 @@ bool JSArray::SetLengthWouldNormalize(Heap* heap, uint32_t new_length) {
   return new_length > kMaxFastArrayLength;
 }
 
-bool JSArray::AllowsSetLength() {
-  bool result = elements().IsFixedArray() || elements().IsFixedDoubleArray();
-  DCHECK(result == !HasTypedArrayElements());
-  return result;
-}
-
 void JSArray::SetContent(Handle<JSArray> array,
                          Handle<FixedArrayBase> storage) {
   EnsureCanContainElements(array, storage, storage->length(),

src/objects/js-array.h

@@ -57,8 +57,6 @@ class JSArray : public TorqueGeneratedJSArray<JSArray, JSObject> {
   static inline bool SetLengthWouldNormalize(Heap* heap, uint32_t new_length);
 
   // Initializes the array to a certain length.
-  inline bool AllowsSetLength();
-
   V8_EXPORT_PRIVATE static Maybe<bool> SetLength(Handle<JSArray> array,
                                                  uint32_t length);
 

src/objects/objects.cc

@@ -5192,8 +5192,6 @@ void JSArray::Initialize(Handle<JSArray> array, int capacity, int length) {
 }
 
 Maybe<bool> JSArray::SetLength(Handle<JSArray> array, uint32_t new_length) {
-  // We should never end in here with a pixel or external array.
-  DCHECK(array->AllowsSetLength());
   if (array->SetLengthWouldNormalize(new_length)) {
     JSObject::NormalizeElements(array);
   }