[heap] Do not invoke ResetPendingObject() in StartMarking()

It is not allowed to invoke ResetPendingObject() in
MarkCompactCollector::StartMarking(). This method is invoked when
starting incremental marking, at this point the object might not be
initialized.

Bug: v8:10315
Change-Id: I7659855d78fbb28536f57b26e8a7d33c1ba4092e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2424267Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70059}

src/heap/mark-compact.cc

@@ -510,9 +510,6 @@ bool MarkCompactCollector::StartCompaction() {
 }
 
 void MarkCompactCollector::StartMarking() {
-  if (FLAG_concurrent_marking || FLAG_parallel_marking) {
-    heap_->new_lo_space()->ResetPendingObject();
-  }
   std::vector<Address> contexts =
       heap()->memory_measurement()->StartProcessing();
   if (FLAG_stress_per_context_marking_worklist) {