cppgc-js: Fix DCHECK around completing sweeping

We only complete sweeping when the young generation GC is enabled.

Change-Id: I915acce35d6ba16716c2c4ee4130f99af0744f83
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3900377Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83269}

src/heap/cppgc-js/cpp-heap.cc

@@ -773,8 +773,6 @@ void CppHeap::TraceEpilogue() {
 }
 
 void CppHeap::RunMinorGC(StackState stack_state) {
-  DCHECK(!sweeper_.IsSweepingInProgress());
-
   if (!generational_gc_supported()) return;
   if (in_no_gc_scope()) return;
   // Minor GC does not support nesting in full GCs.
@@ -782,6 +780,8 @@ void CppHeap::RunMinorGC(StackState stack_state) {
   // Minor GCs with the stack are currently not supported.
   if (stack_state == StackState::kMayContainHeapPointers) return;
 
+  DCHECK(!sweeper_.IsSweepingInProgress());
+
   // Notify GC tracer that CppGC started young GC cycle.
   isolate_->heap()->tracer()->NotifyYoungCppGCRunning();