[runtime] Allocate space for computed property names

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 93eacb292fdafd938cd1c141d6514d05724c98ea..6e4c80722058fcfd46ca6c9c0aca754d84bc914f 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9827,6 +9827,45 @@ void FixedArray::CopyTo(int pos, FixedArray* dest, int dest_pos, int len) {
   }
 }
 
+Object* BoilerplateDescription::name(int index) const {
+  // get() already checks for out of bounds access, but we do not want to allow
+  // access to the last element, if it is the number of properties.
+  DCHECK_NE(size(), index);
+  return get(2 * index);
+}
+
+Object* BoilerplateDescription::value(int index) const {
+  return get(2 * index + 1);
+}
+
+int BoilerplateDescription::size() const {
+  DCHECK_EQ(0, (length() - (this->has_number_of_properties() ? 1 : 0)) % 2);
+  // Rounding is intended.
+  return length() / 2;
+}
+
+int BoilerplateDescription::backing_store_size() const {
+  if (has_number_of_properties()) {
+    // If present, the last entry contains the number of properties.
+    return Smi::cast(this->get(length() - 1))->value();
+  }
+  // If the number is not given explicitly, we assume there are no
+  // properties with computed names.
+  return size();
+}
+
+void BoilerplateDescription::set_backing_store_size(Isolate* isolate,
+                                                    int backing_store_size) {
+  DCHECK(has_number_of_properties());
+  DCHECK_NE(size(), backing_store_size);
+  Handle<Object> backing_store_size_obj =
+      isolate->factory()->NewNumberFromInt(backing_store_size);
+  set(length() - 1, *backing_store_size_obj);
+}
+
+bool BoilerplateDescription::has_number_of_properties() const {
+  return length() % 2 != 0;
+}
 
 #ifdef DEBUG
 bool FixedArray::IsEqualTo(FixedArray* other) {