Propagate writing-mode from the first region to the flow thread.

Source/core/rendering/RenderFlowThread.cpp

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 66 matching lines @@
     newStyle->font().update(0);
 
     return newStyle.release();
 }
 
 void RenderFlowThread::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
 {
     RenderBlock::styleDidChange(diff, oldStyle);
 
     if (oldStyle && oldStyle->writingMode() != style()->writingMode())
-        m_regionsInvalidated = true;
+        invalidateRegions();
 }
 
 void RenderFlowThread::removeFlowChildInfo(RenderObject* child)
 {
     if (child->isBox())
         removeRenderBoxRegionInfo(toRenderBox(child));
     clearRenderObjectCustomStyle(child);
 }
 
 void RenderFlowThread::addRegionToThread(RenderRegion* renderRegion)
@@ skipping 945 matching lines @@
 {
     if (!m_renderFlowThread)
         return;
     RenderView* view = m_renderFlowThread->view();
     ASSERT(view->flowThreadController()->currentRenderFlowThread() == m_renderFlowThread);
     view->flowThreadController()->setCurrentRenderFlowThread(m_previousRenderFlowThread);
 }
 
 
 } // namespace WebCore