Compact weak fixed arrays before serializing.

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 8277 matching lines @@
   Handle<WeakFixedArray> new_array =
       Allocate(array->GetIsolate(), new_length, array);
   if (FLAG_trace_weak_arrays) {
     PrintF("[WeakFixedArray: growing to size %d ]\n", new_length);
   }
   WeakFixedArray::Set(new_array, array->Length(), value);
   return new_array;
 }
 
 
+void WeakFixedArray::Compact() {
+  FixedArray* array = FixedArray::cast(this);
+  int new_length = kFirstIndex;
+  for (int i = kFirstIndex; i < array->length(); i++) {
+    Object* element = array->get(i);
+    if (element->IsSmi()) continue;
+    if (WeakCell::cast(element)->cleared()) continue;
+    array->set(new_length++, element);
+  }
+  array->Shrink(new_length);
+  set_last_used_index(0);
+}
+
+
 void WeakFixedArray::Remove(Handle<HeapObject> value) {
   // Optimize for the most recently added element to be removed again.
   int first_index = last_used_index();
   for (int i = first_index;;) {
     if (Get(i) == *value) {
       clear(i);
       // Users of WeakFixedArray should make sure that there are no duplicates,
       // they can use Add(..., kAddIfNotFound) if necessary.
       return;
     }
@@ skipping 8782 matching lines @@
   if (!invalidate && old_type == PropertyCellType::kConstant &&
       new_type != PropertyCellType::kConstant) {
     auto isolate = dictionary->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
   return value;
 }
 
 } }  // namespace v8::internal