[heap] Remove black pages and use black areas instead.

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 6a238839b18eb55d6139f1d83cc159a85343532c..01170333d7bc6b421e4a294d7d278b5a72cbaa74 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -218,7 +218,19 @@ class MarkBitCellIterator BASE_EMBEDDED {
 
   inline void Advance() {
     cell_index_++;
-    cell_base_ += 32 * kPointerSize;
+    cell_base_ += Bitmap::kBitsPerCell * kPointerSize;
+  }
+
+  inline bool Advance(unsigned int new_cell_index) {
+    if (new_cell_index != cell_index_) {
+      DCHECK_GT(new_cell_index, cell_index_);
+      DCHECK_LE(new_cell_index, last_cell_index_);
+      unsigned int diff = new_cell_index - cell_index_;
+      cell_index_ = new_cell_index;
+      cell_base_ += diff * (Bitmap::kBitsPerCell * kPointerSize);
+      return true;
+    }
+    return false;
   }
 
   // Return the next mark bit cell. If there is no next it returns 0;
@@ -253,8 +265,6 @@ class LiveObjectIterator BASE_EMBEDDED {
         it_(chunk_),
         cell_base_(it_.CurrentCellBase()),
         current_cell_(*it_.CurrentCell()) {
-    // Black pages can not be iterated.
-    DCHECK(!chunk->IsFlagSet(Page::BLACK_PAGE));
   }
 
   HeapObject* Next();