[heap] RecordWrites iterates black object to ensure marking progress.

src/heap/mark-compact.h

 // 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.
 
 #ifndef V8_HEAP_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
@@ skipping 352 matching lines @@
   unsigned int last_cell_index_;
   unsigned int cell_index_;
   Address cell_base_;
 };
 
 // Grey objects can happen on black pages when black objects transition to
 // grey e.g. when calling RecordWrites on them.
 enum LiveObjectIterationMode {
   kBlackObjects,
   kGreyObjects,
-  kGreyObjectsOnBlackPage,
   kAllLiveObjects
 };
 
 template <LiveObjectIterationMode T>
 class LiveObjectIterator BASE_EMBEDDED {
  public:
   explicit LiveObjectIterator(MemoryChunk* chunk)
       : chunk_(chunk),
         it_(chunk_),
         cell_base_(it_.CurrentCellBase()),
         current_cell_(*it_.CurrentCell()) {
-    // Black pages can only be iterated with kGreyObjectsOnBlackPage mode.
-    if (T != kGreyObjectsOnBlackPage) {
-      DCHECK(!chunk->IsFlagSet(Page::BLACK_PAGE));
-    }
+    // Black pages can not be iterated.
+    DCHECK(!chunk->IsFlagSet(Page::BLACK_PAGE));
   }
 
   HeapObject* Next();
 
  private:
   MemoryChunk* chunk_;
   MarkBitCellIterator it_;
   Address cell_base_;
   MarkBit::CellType current_cell_;
 };
@@ skipping 303 matching lines @@
 
   // Refill the marking stack with overflowed objects from the heap.  This
   // function either leaves the marking stack full or clears the overflow
   // flag on the marking stack.
   void RefillMarkingDeque();
 
   // Helper methods for refilling the marking stack by discovering grey objects
   // on various pages of the heap. Used by {RefillMarkingDeque} only.
   template <class T>
   void DiscoverGreyObjectsWithIterator(T* it);
-  template <LiveObjectIterationMode T>
   void DiscoverGreyObjectsOnPage(MemoryChunk* p);
   void DiscoverGreyObjectsInSpace(PagedSpace* space);
   void DiscoverGreyObjectsInNewSpace();
 
   // Callback function for telling whether the object *p is an unmarked
   // heap object.
   static bool IsUnmarkedHeapObject(Object** p);
 
   // Clear non-live references in weak cells, transition and descriptor arrays,
   // and deoptimize dependent code of non-live maps.
@@ skipping 141 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_