cppgc: Fix marking on allocation

Marking on allocation assumes a non-empty stack. Thus marking on
allocation will not finalize even if it runs out of work (we prefer
to finalize in a non-nestable task with no stack).
Instead it will schedule another marking task and delegates
finalization to the next marking task.

Bug: chromium:1056170
Change-Id: I457090fe0a235707bb9973e330ff24fb25ac66c0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2366764Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69534}

src/heap/cppgc/marker.cc

@@ -290,7 +290,13 @@ bool MarkerBase::IncrementalMarkingStep(MarkingConfig::StackState stack_state,
 
 bool MarkerBase::AdvanceMarkingOnAllocation() {
   // Replace with schedule based deadline.
-  return AdvanceMarkingWithDeadline(kMinimumMarkedBytesPerIncrementalStep);
+  bool is_done =
+      AdvanceMarkingWithDeadline(kMinimumMarkedBytesPerIncrementalStep);
+  if (is_done) {
+    // Schedule another incremental task for finalizing without a stack.
+    ScheduleIncrementalMarkingTask();
+  }
+  return is_done;
 }
 
 bool MarkerBase::AdvanceMarkingWithDeadline(size_t expected_marked_bytes,