[heap] Fix regression around GC request via stack guard

When a GC was requested via stack guard, we don't restart incremental
marking anymore on finding new objects but rather finish the GC cycle.

This regressed in https://crrev.com/c/3702801

Bug: v8:12985, chromium:1338071, v8:12775
Change-Id: Ie515cea6d5345ad1111a4fb9f042cffc52083453
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3716486Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81291}

src/heap/heap.cc

@@ -1529,7 +1529,7 @@ void Heap::HandleGCRequest() {
     CheckMemoryPressure();
   } else if (CollectionRequested()) {
     CheckCollectionRequested();
-  } else if (incremental_marking()->IsComplete()) {
+  } else if (incremental_marking()->CollectionRequested()) {
     CollectAllGarbage(current_gc_flags_,
                       GarbageCollectionReason::kFinalizeMarkingViaStackGuard,
                       current_gc_callback_flags_);

src/heap/incremental-marking.cc

@@ -524,7 +524,9 @@ bool IncrementalMarking::Stop() {
     }
   }
 
+  collection_requested_ = false;
   heap_->isolate()->stack_guard()->ClearGC();
+
   SetState(STOPPED);
   is_compacting_ = false;
   FinishBlackAllocation();
@@ -608,6 +610,7 @@ void IncrementalMarking::MarkingComplete(CompletionAction action) {
   }
 
   if (action == CompletionAction::kGcViaStackGuard) {
+    collection_requested_ = true;
     heap_->isolate()->stack_guard()->RequestGC();
   }
 }

src/heap/incremental-marking.h

@@ -105,6 +105,8 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
   bool IsMarking() const { return state() >= MARKING; }
   bool IsComplete() const { return state() == COMPLETE; }
 
+  bool CollectionRequested() const { return collection_requested_; }
+
   bool CanBeActivated();
   bool WasActivated();
 
@@ -269,6 +271,7 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
   bool is_compacting_ = false;
   bool was_activated_ = false;
   bool black_allocation_ = false;
+  bool collection_requested_ = false;
   IncrementalMarkingJob incremental_marking_job_;
 
   Observer new_generation_observer_;