Reland "Keep track of array buffers in new space separately"

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 10a83fadbe58ecbe571ff03c269e84bf0b1a8338..664b80e38a7d4f7f11f37681a7b362eec2aa3d74 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6560,7 +6560,8 @@ v8::ArrayBuffer::Contents v8::ArrayBuffer::Externalize() {
   Utils::ApiCheck(!self->is_external(), "v8::ArrayBuffer::Externalize",
                   "ArrayBuffer already externalized");
   self->set_is_external(true);
-  isolate->heap()->UnregisterArrayBuffer(self->backing_store());
+  isolate->heap()->UnregisterArrayBuffer(isolate->heap()->InNewSpace(*self),
+                                         self->backing_store());
 
   return GetContents();
 }
@@ -6767,7 +6768,8 @@ v8::SharedArrayBuffer::Contents v8::SharedArrayBuffer::Externalize() {
   Utils::ApiCheck(!self->is_external(), "v8::SharedArrayBuffer::Externalize",
                   "SharedArrayBuffer already externalized");
   self->set_is_external(true);
-  isolate->heap()->UnregisterArrayBuffer(self->backing_store());
+  isolate->heap()->UnregisterArrayBuffer(isolate->heap()->InNewSpace(*self),
+                                         self->backing_store());
   return GetContents();
 }