[heap] Iterate handles with special left-trim visitor

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 1395 matching lines @@
   // Skip the weak next code link in a code object, which is visited in
   // ProcessTopOptimizedFrame.
   void VisitNextCodeLink(Object** p) override {}
 
  private:
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     HeapObject* object = HeapObject::cast(*p);
 
-    if (collector_->heap()->PurgeLeftTrimmedObject(p)) return;
-
     MarkBit mark_bit = Marking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;
 
     Map* map = object->map();
     // Mark the object.
     collector_->SetMark(object, mark_bit);
 
     // Mark the map pointer and body, and push them on the marking stack.
     MarkBit map_mark = Marking::MarkBitFrom(map);
     collector_->MarkObject(map, map_mark);
@@ skipping 2668 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8