Introduce lazy sweeping.

src/incremental-marking-inl.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 17 matching lines @@
 #ifndef V8_INCREMENTAL_MARKING_INL_H_
 #define V8_INCREMENTAL_MARKING_INL_H_
 
 #include "incremental-marking.h"
 
 namespace v8 {
 namespace internal {
 
 
 void IncrementalMarking::RecordWrite(HeapObject* obj, Object* value) {
-  if (!IsStopped() && value->IsHeapObject()) {
+  if (IsMarking() && value->IsHeapObject()) {
     MarkBit value_bit = heap_->marking()->MarkBitFrom(HeapObject::cast(value));
     if (IsWhite(value_bit)) {
       MarkBit obj_bit = heap_->marking()->MarkBitFrom(obj);
       if (IsBlack(obj_bit)) {
         BlackToGreyAndUnshift(obj, obj_bit);
         RestartIfNotMarking();
       }
     }
   }
 }
 
 
 void IncrementalMarking::RecordWriteOf(HeapObject* value) {
-  if (state_ != STOPPED) {
+  if (IsMarking()) {
     MarkBit value_bit = heap_->marking()->MarkBitFrom(value);
     if (IsWhite(value_bit)) {
       WhiteToGreyAndPush(value, value_bit);
       RestartIfNotMarking();
     }
   }
 }
 
 
 void IncrementalMarking::RecordWrites(HeapObject* obj) {
-  if (!IsStopped()) {
+  if (IsMarking()) {
     MarkBit obj_bit = heap_->marking()->MarkBitFrom(obj);
     if (IsBlack(obj_bit)) {
       BlackToGreyAndUnshift(obj, obj_bit);
       RestartIfNotMarking();
     }
   }
 }
 
 
 void IncrementalMarking::BlackToGreyAndUnshift(HeapObject* obj,
@@ skipping 34 matching lines @@
   if (IsWhite(mark_bit)) return WHITE_OBJECT;
   if (IsGrey(mark_bit)) return GREY_OBJECT;
   UNREACHABLE();
   return IMPOSSIBLE_COLOR;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_INCREMENTAL_MARKING_INL_H_