Revert "Precisely sweep scan on scavenge pages and use heap iterator to iterate over them."

This reverts r22154.

TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/365853003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22159 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mark-compact.cc

@@ -4145,16 +4145,6 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
           SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
           pages_swept++;
           parallel_sweeping_active = true;
-        } else {
-          if (p->scan_on_scavenge()) {
-            SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(
-                space, p, NULL);
-            pages_swept++;
-            if (FLAG_gc_verbose) {
-              PrintF("Sweeping 0x%" V8PRIxPTR
-                  " scan on scavenge page precisely.\n",
-                  reinterpret_cast<intptr_t>(p));
-            }
         } else {
           if (FLAG_gc_verbose) {
             PrintF("Sweeping 0x%" V8PRIxPTR " conservatively in parallel.\n",
@@ -4163,7 +4153,6 @@ void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
           p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
           space->IncreaseUnsweptFreeBytes(p);
         }
-        }
         space->set_end_of_unswept_pages(p);
         break;
       }

src/store-buffer.cc

@@ -552,21 +552,8 @@ void StoreBuffer::IteratePointersToNewSpace(ObjectSlotCallback slot_callback,
             FindPointersToNewSpaceInMapsRegion(
                 start, end, slot_callback, clear_maps);
           } else {
-            ASSERT(page->WasSweptPrecisely());
-            HeapObjectIterator iterator(page, NULL);
-            for (HeapObject* heap_object = iterator.Next();
-                 heap_object != NULL;
-                 heap_object = iterator.Next()) {
-              // We skip filler, free space, and constant pool objects.
-              if (!heap_object->IsFiller() &&
-                  !heap_object->IsConstantPoolArray()) {
             FindPointersToNewSpaceInRegion(
-                    heap_object->address() + HeapObject::kHeaderSize,
-                    heap_object->address() + heap_object->Size(),
-                    slot_callback,
-                    clear_maps);
-              }
-            }
+                start, end, slot_callback, clear_maps);
           }
         }
       }