Introduce phantom weak handles in the API and use them internally for debug info

src/api.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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 472 matching lines @@
 
 i::Object** V8::CopyPersistent(i::Object** obj) {
   i::Handle<i::Object> result = i::GlobalHandles::CopyGlobal(obj);
 #ifdef DEBUG
   (*obj)->ObjectVerify();
 #endif  // DEBUG
   return result.location();
 }
 
 
-void V8::MakeWeak(i::Object** object,
-                  void* parameters,
-                  WeakCallback weak_callback) {
-  i::GlobalHandles::MakeWeak(object, parameters, weak_callback);
+void V8::MakeWeak(i::Object** object, void* parameters,
+                  WeakCallback weak_callback, V8::WeakHandleType weak_type) {
+  i::GlobalHandles::PhantomState phantom;
+  phantom = weak_type == V8::PhantomHandle ? i::GlobalHandles::Phantom
+                                           : i::GlobalHandles::Nonphantom;
+  i::GlobalHandles::MakeWeak(object, parameters, weak_callback, phantom);
 }
 
 
 void* V8::ClearWeak(i::Object** obj) {
   return i::GlobalHandles::ClearWeakness(obj);
 }
 
 
 void V8::DisposeGlobal(i::Object** obj) {
   i::GlobalHandles::Destroy(obj);
@@ skipping 7252 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal