Fix corner-case in heap size estimation.

src/spaces.cc

 // 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 863 matching lines @@
     first_unswept_page_ = page->next_page();
     if (first_unswept_page_ == anchor()) {
       first_unswept_page_ = Page::FromAddress(NULL);
     }
   }
 
   if (page->WasSwept()) {
     intptr_t size = free_list_.EvictFreeListItems(page);
     accounting_stats_.AllocateBytes(size);
     ASSERT_EQ(Page::kObjectAreaSize, static_cast<int>(size));
+  } else {
+    DecreaseUnsweptFreeBytes(page);
   }
 
   if (Page::FromAllocationTop(allocation_info_.top) == page) {
     allocation_info_.top = allocation_info_.limit = NULL;
   }
 
   intptr_t size = page->ObjectAreaEnd() - page->ObjectAreaStart();
 
   page->Unlink();
   if (page->IsFlagSet(MemoryChunk::CONTAINS_ONLY_DATA)) {
@@ skipping 1379 matching lines @@
 
   intptr_t freed_bytes = 0;
   Page* p = first_unswept_page_;
   do {
     Page* next_page = p->next_page();
     if (ShouldBeSweptLazily(p)) {
       if (FLAG_gc_verbose) {
         PrintF("Sweeping 0x%" V8PRIxPTR " lazily advanced.\n",
                reinterpret_cast<intptr_t>(p));
       }
-      unswept_free_bytes_ -= (Page::kObjectAreaSize - p->LiveBytes());
+      DecreaseUnsweptFreeBytes(p);
       freed_bytes += MarkCompactCollector::SweepConservatively(this, p);
     }
     p = next_page;
   } while (p != anchor() && freed_bytes < bytes_to_sweep);
 
   if (p == anchor()) {
     first_unswept_page_ = Page::FromAddress(NULL);
   } else {
     first_unswept_page_ = p;
   }
@@ skipping 536 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal