LibJS: Always collect all garbage when destroying Heap

When the Heap is going down, it's our last chance to run destructors,
so add a separate collector mode where we simply skip over the marking
phase and go directly to sweeping. This causes everything to get swept
and all live cells get destroyed.

This way, valgrind reports 0 leaks on exit. :^)

1 files changed, 7 insertions, 4 deletions

diff --git a/Libraries/LibJS/Heap/Heap.cpp b/Libraries/LibJS/Heap/Heap.cpp
index 4ad48b5a97..b3853680c4 100644
--- a/Libraries/LibJS/Heap/Heap.cpp
+++ b/Libraries/LibJS/Heap/Heap.cpp
@@ -51,6 +51,7 @@ Heap::Heap(Interpreter& interpreter)
 
 Heap::~Heap()
 {
+    collect_garbage(CollectionType::CollectEverything);
 }
 
 Cell* Heap::allocate_cell(size_t size)
@@ -72,11 +73,13 @@ Cell* Heap::allocate_cell(size_t size)
     return cell;
 }
 
-void Heap::collect_garbage()
+void Heap::collect_garbage(CollectionType collection_type)
 {
-    HashTable<Cell*> roots;
-    gather_roots(roots);
-    mark_live_cells(roots);
+    if (collection_type == CollectionType::CollectGarbage) {
+        HashTable<Cell*> roots;
+        gather_roots(roots);
+        mark_live_cells(roots);
+    }
     sweep_dead_cells();
 }