[heap] Start concurrent marking simultaneously with incremental marking.

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 <deque>
 
 #include "src/base/bits.h"
@@ skipping 168 matching lines @@
     if (IsFull()) {
       SetOverflowed();
       return false;
     } else {
       bottom_ = ((bottom_ - 1) & mask_);
       array_[bottom_] = object;
       return true;
     }
   }
 
+  template <typename Callback>
+  void Iterate(Callback callback) {
+    int i = bottom_;
+    while (i != top_) {
+      callback(array_[i]);
+      i = (i + 1) & mask_;
+    }
+  }
+
   HeapObject** array() { return array_; }
   int bottom() { return bottom_; }
   int top() { return top_; }
   int mask() { return mask_; }
   void set_top(int top) { top_ = top; }
 
  private:
   // This task uncommits the marking_deque backing store if
   // markin_deque->in_use_ is false.
   class UncommitTask : public CancelableTask {
@@ skipping 662 matching lines @@
 
  private:
   MarkCompactCollector* collector_;
 };
 
 V8_EXPORT_PRIVATE const char* AllocationSpaceName(AllocationSpace space);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_