Begin tracking why layout is invalidated

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 443 matching lines @@
     ResourceCacheValidationSuppressor validationSuppressor(document()->fetcher());
 
     document()->setPrinting(printing);
     view()->adjustMediaTypeForPrinting(printing);
 
     document()->styleResolverChanged();
     if (shouldUsePrintingLayout()) {
         view()->forceLayoutForPagination(pageSize, originalPageSize, maximumShrinkRatio);
     } else {
         if (LayoutView* layoutView = view()->layoutView())
-            layoutView->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation();
+            layoutView->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation(LayoutInvalidationReason::PrintingChanged);
         view()->layout();
         view()->adjustViewSize();
     }
 
     // Subframes of the one we're printing don't lay out to the page size.
     for (RefPtrWillBeRawPtr<Frame> child = tree().firstChild(); child; child = child->tree().nextSibling()) {
         if (child->isLocalFrame())
             toLocalFrame(child.get())->setPrinting(printing, FloatSize(), FloatSize(), 0);
     }
 }
@@ skipping 364 matching lines @@
     // We detach the FrameView's custom scroll bars as early as
     // possible to prevent m_doc->detach() from messing with the view
     // such that its scroll bars won't be torn down.
     //
     // FIXME: We should revisit this.
     if (m_view)
         m_view->prepareForDetach();
 }
 
 } // namespace blink