Fix bug introduced by r21269.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 114 matching lines @@
 }
 
 
 PageSpace::~PageSpace() {
   FreePages(pages_);
   FreePages(large_pages_);
 }
 
 
 intptr_t PageSpace::LargePageSizeFor(intptr_t size) {
-  intptr_t page_size = Utils::RoundUp(size + sizeof(HeapPage),
+  intptr_t page_size = Utils::RoundUp(size + HeapPage::ObjectStartOffset(),
                                       VirtualMemory::PageSize());
   return page_size;
 }
 
 
 HeapPage* PageSpace::AllocatePage(HeapPage::PageType type) {
   HeapPage* page = HeapPage::Allocate(kPageSize, type);
   if (pages_ == NULL) {
     pages_ = page;
   } else {
@@ skipping 471 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result= static_cast<int>((static_cast<double>(gc_time) /
                              static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart