Implement lazy block layout prototype behind a runtime flag.

Source/core/rendering/style/RenderStyleConstants.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 415 matching lines @@
 
 // The order of this enum must match the order of the display values in CSSValueKeywords.in.
 enum EDisplay {
     INLINE, BLOCK, LIST_ITEM, RUN_IN, COMPACT, INLINE_BLOCK,
     TABLE, INLINE_TABLE, TABLE_ROW_GROUP,
     TABLE_HEADER_GROUP, TABLE_FOOTER_GROUP, TABLE_ROW,
     TABLE_COLUMN_GROUP, TABLE_COLUMN, TABLE_CELL,
     TABLE_CAPTION, BOX, INLINE_BOX,
     FLEX, INLINE_FLEX,
     GRID, INLINE_GRID,
+    LAZY_BLOCK,
     NONE
 };
 
 enum EInsideLink {
     NotInsideLink, InsideUnvisitedLink, InsideVisitedLink
 };
     
 enum EPointerEvents {
     PE_NONE, PE_AUTO, PE_STROKE, PE_FILL, PE_PAINTED, PE_VISIBLE,
     PE_VISIBLE_STROKE, PE_VISIBLE_FILL, PE_VISIBLE_PAINTED, PE_ALL
@@ skipping 54 matching lines @@
 // Reasonable maximum to prevent insane font sizes from causing crashes on some platforms (such as Windows).
 static const float maximumAllowedFontSize = 1000000.0f;
 
 #if ENABLE(CSS3_TEXT)
 enum TextIndentLine { TextIndentFirstLine, TextIndentEachLine };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderStyleConstants_h