Revert of Blink-compatible serialization of arrays, both dense and sparse.

src/value-serializer.cc

Index: src/value-serializer.cc
diff --git a/src/value-serializer.cc b/src/value-serializer.cc
index 2689fa0bf3e387784e091459c3db159e7db45a3d..ad7492a2a60f32c03ca30b4808fb8954c3f95fb1 100644
--- a/src/value-serializer.cc
+++ b/src/value-serializer.cc
@@ -60,16 +60,6 @@
   kBeginJSObject = 'o',
   // End of a JS object. numProperties:uint32_t
   kEndJSObject = '{',
-  // Beginning of a sparse JS array. length:uint32_t
-  // Elements and properties are written as key/value pairs, like objects.
-  kBeginSparseJSArray = 'a',
-  // End of a sparse JS array. numProperties:uint32_t length:uint32_t
-  kEndSparseJSArray = '@',
-  // Beginning of a dense JS array. length:uint32_t
-  // |length| elements, followed by properties as key/value pairs
-  kBeginDenseJSArray = 'A',
-  // End of a dense JS array. numProperties:uint32_t length:uint32_t
-  kEndDenseJSArray = '$',
 };
 
 ValueSerializer::ValueSerializer(Isolate* isolate)
@@ -263,8 +253,6 @@
 
   HandleScope scope(isolate_);
   switch (instance_type) {
-    case JS_ARRAY_TYPE:
-      return WriteJSArray(Handle<JSArray>::cast(receiver));
     case JS_OBJECT_TYPE:
     case JS_API_OBJECT_TYPE:
       return WriteJSObject(Handle<JSObject>::cast(receiver));
@@ -287,67 +275,6 @@
   }
   WriteTag(SerializationTag::kEndJSObject);
   WriteVarint<uint32_t>(properties_written);
-  return Just(true);
-}
-
-Maybe<bool> ValueSerializer::WriteJSArray(Handle<JSArray> array) {
-  uint32_t length;
-  array->length()->ToArrayLength(&length);
-
-  // To keep things simple, for now we decide between dense and sparse
-  // serialization based on elements kind. A more principled heuristic could
-  // count the elements, but would need to take care to note which indices
-  // existed (as only indices which were enumerable own properties at this point
-  // should be serialized).
-  const bool should_serialize_densely =
-      array->HasFastElements() && !array->HasFastHoleyElements();
-
-  if (should_serialize_densely) {
-    // TODO(jbroman): Distinguish between undefined and a hole (this can happen
-    // if serializing one of the elements deletes another). This requires wire
-    // format changes.
-    WriteTag(SerializationTag::kBeginDenseJSArray);
-    WriteVarint<uint32_t>(length);
-    for (uint32_t i = 0; i < length; i++) {
-      // Serializing the array's elements can have arbitrary side effects, so we
-      // cannot rely on still having fast elements, even if it did to begin
-      // with.
-      Handle<Object> element;
-      LookupIterator it(isolate_, array, i, array, LookupIterator::OWN);
-      if (!Object::GetProperty(&it).ToHandle(&element) ||
-          !WriteObject(element).FromMaybe(false)) {
-        return Nothing<bool>();
-      }
-    }
-    KeyAccumulator accumulator(isolate_, KeyCollectionMode::kOwnOnly,
-                               ENUMERABLE_STRINGS);
-    if (!accumulator.CollectOwnPropertyNames(array, array).FromMaybe(false)) {
-      return Nothing<bool>();
-    }
-    Handle<FixedArray> keys =
-        accumulator.GetKeys(GetKeysConversion::kConvertToString);
-    uint32_t properties_written;
-    if (!WriteJSObjectProperties(array, keys).To(&properties_written)) {
-      return Nothing<bool>();
-    }
-    WriteTag(SerializationTag::kEndDenseJSArray);
-    WriteVarint<uint32_t>(properties_written);
-    WriteVarint<uint32_t>(length);
-  } else {
-    WriteTag(SerializationTag::kBeginSparseJSArray);
-    WriteVarint<uint32_t>(length);
-    Handle<FixedArray> keys;
-    uint32_t properties_written;
-    if (!KeyAccumulator::GetKeys(array, KeyCollectionMode::kOwnOnly,
-                                 ENUMERABLE_STRINGS)
-             .ToHandle(&keys) ||
-        !WriteJSObjectProperties(array, keys).To(&properties_written)) {
-      return Nothing<bool>();
-    }
-    WriteTag(SerializationTag::kEndSparseJSArray);
-    WriteVarint<uint32_t>(properties_written);
-    WriteVarint<uint32_t>(length);
-  }
   return Just(true);
 }
 
@@ -527,10 +454,6 @@
     }
     case SerializationTag::kBeginJSObject:
       return ReadJSObject();
-    case SerializationTag::kBeginSparseJSArray:
-      return ReadSparseJSArray();
-    case SerializationTag::kBeginDenseJSArray:
-      return ReadDenseJSArray();
     default:
       return MaybeHandle<Object>();
   }
@@ -592,71 +515,6 @@
 
   DCHECK(HasObjectWithID(id));
   return scope.CloseAndEscape(object);
-}
-
-MaybeHandle<JSArray> ValueDeserializer::ReadSparseJSArray() {
-  // If we are at the end of the stack, abort. This function may recurse.
-  if (StackLimitCheck(isolate_).HasOverflowed()) return MaybeHandle<JSArray>();
-
-  uint32_t length;
-  if (!ReadVarint<uint32_t>().To(&length)) return MaybeHandle<JSArray>();
-
-  uint32_t id = next_id_++;
-  HandleScope scope(isolate_);
-  Handle<JSArray> array = isolate_->factory()->NewJSArray(0);
-  JSArray::SetLength(array, length);
-  AddObjectWithID(id, array);
-
-  uint32_t num_properties;
-  uint32_t expected_num_properties;
-  uint32_t expected_length;
-  if (!ReadJSObjectProperties(array, SerializationTag::kEndSparseJSArray)
-           .To(&num_properties) ||
-      !ReadVarint<uint32_t>().To(&expected_num_properties) ||
-      !ReadVarint<uint32_t>().To(&expected_length) ||
-      num_properties != expected_num_properties || length != expected_length) {
-    return MaybeHandle<JSArray>();
-  }
-
-  DCHECK(HasObjectWithID(id));
-  return scope.CloseAndEscape(array);
-}
-
-MaybeHandle<JSArray> ValueDeserializer::ReadDenseJSArray() {
-  // If we are at the end of the stack, abort. This function may recurse.
-  if (StackLimitCheck(isolate_).HasOverflowed()) return MaybeHandle<JSArray>();
-
-  uint32_t length;
-  if (!ReadVarint<uint32_t>().To(&length)) return MaybeHandle<JSArray>();
-
-  uint32_t id = next_id_++;
-  HandleScope scope(isolate_);
-  Handle<JSArray> array = isolate_->factory()->NewJSArray(
-      FAST_HOLEY_ELEMENTS, length, length, INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
-  AddObjectWithID(id, array);
-
-  Handle<FixedArray> elements(FixedArray::cast(array->elements()), isolate_);
-  for (uint32_t i = 0; i < length; i++) {
-    Handle<Object> element;
-    if (!ReadObject().ToHandle(&element)) return MaybeHandle<JSArray>();
-    // TODO(jbroman): Distinguish between undefined and a hole.
-    if (element->IsUndefined(isolate_)) continue;
-    elements->set(i, *element);
-  }
-
-  uint32_t num_properties;
-  uint32_t expected_num_properties;
-  uint32_t expected_length;
-  if (!ReadJSObjectProperties(array, SerializationTag::kEndDenseJSArray)
-           .To(&num_properties) ||
-      !ReadVarint<uint32_t>().To(&expected_num_properties) ||
-      !ReadVarint<uint32_t>().To(&expected_length) ||
-      num_properties != expected_num_properties || length != expected_length) {
-    return MaybeHandle<JSArray>();
-  }
-
-  DCHECK(HasObjectWithID(id));
-  return scope.CloseAndEscape(array);
 }
 
 Maybe<uint32_t> ValueDeserializer::ReadJSObjectProperties(