[heap] Filter out stale left-trimmed handles

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index e724ea420a4cd9c5fe77e83c0c03df291ad5a01a..f7dc451efaea61504113b699334aca4e8bd444b3 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -3160,10 +3160,6 @@ FixedArrayBase* Heap::LeftTrimFixedArray(FixedArrayBase* object,
   DCHECK(!lo_space()->Contains(object));
   DCHECK(object->map() != fixed_cow_array_map());
 
-  // Ensure that the no handle-scope has more than one pointer to the same
-  // backing-store.
-  SLOW_DCHECK(CountHandlesForObject(object) <= 1);
-
   STATIC_ASSERT(FixedArrayBase::kMapOffset == 0);
   STATIC_ASSERT(FixedArrayBase::kLengthOffset == kPointerSize);
   STATIC_ASSERT(FixedArrayBase::kHeaderSize == 2 * kPointerSize);
@@ -5723,32 +5719,6 @@ void Heap::PrintHandles() {
 
 #endif
 
-#ifdef ENABLE_SLOW_DCHECKS
-
-class CountHandleVisitor : public ObjectVisitor {
- public:
-  explicit CountHandleVisitor(Object* object) : object_(object) {}
-
-  void VisitPointers(Object** start, Object** end) override {
-    for (Object** p = start; p < end; p++) {
-      if (object_ == reinterpret_cast<Object*>(*p)) count_++;
-    }
-  }
-
-  int count() { return count_; }
-
- private:
-  Object* object_;
-  int count_ = 0;
-};
-
-int Heap::CountHandlesForObject(Object* object) {
-  CountHandleVisitor v(object);
-  isolate_->handle_scope_implementer()->Iterate(&v);
-  return v.count();
-}
-#endif
-
 class CheckHandleCountVisitor : public ObjectVisitor {
  public:
   CheckHandleCountVisitor() : handle_count_(0) {}