[api] Prototype WeakRef implementation

src/heap/heap.cc

 // Copyright 2012 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 "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/assembler-inl.h"
 #include "src/ast/context-slot-cache.h"
@@ skipping 2771 matching lines @@
   set_string_split_cache(*factory->NewFixedArray(
       RegExpResultsCache::kRegExpResultsCacheSize, TENURED));
   set_regexp_multiple_cache(*factory->NewFixedArray(
       RegExpResultsCache::kRegExpResultsCacheSize, TENURED));
 
   set_undefined_cell(*factory->NewCell(factory->undefined_value()));
 
   // Microtask queue uses the empty fixed array as a sentinel for "empty".
   // Number of queued microtasks stored in Isolate::pending_microtask_count().
   set_microtask_queue(empty_fixed_array());
+  set_weak_refs(empty_fixed_array());
 
   {
     Handle<FixedArray> empty_sloppy_arguments_elements =
         factory->NewFixedArray(2, TENURED);
     empty_sloppy_arguments_elements->set_map(sloppy_arguments_elements_map());
     set_empty_sloppy_arguments_elements(*empty_sloppy_arguments_elements);
   }
 
   {
     Handle<WeakCell> cell = factory->NewWeakCell(factory->undefined_value());
@@ skipping 120 matching lines @@
 bool Heap::RootCanBeWrittenAfterInitialization(Heap::RootListIndex root_index) {
   switch (root_index) {
     case kNumberStringCacheRootIndex:
     case kInstanceofCacheFunctionRootIndex:
     case kInstanceofCacheMapRootIndex:
     case kInstanceofCacheAnswerRootIndex:
     case kCodeStubsRootIndex:
     case kScriptListRootIndex:
     case kMaterializedObjectsRootIndex:
     case kMicrotaskQueueRootIndex:
+    case kWeakRefsRootIndex:
     case kDetachedContextsRootIndex:
     case kWeakObjectToCodeTableRootIndex:
     case kWeakNewSpaceObjectToCodeListRootIndex:
     case kRetainedMapsRootIndex:
     case kCodeCoverageListRootIndex:
     case kNoScriptSharedFunctionInfosRootIndex:
     case kWeakStackTraceListRootIndex:
     case kSerializedTemplatesRootIndex:
     case kSerializedGlobalProxySizesRootIndex:
     case kPublicSymbolTableRootIndex:
@@ skipping 3457 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8