Output object paint invalidation information of sub frames

third_party/WebKit/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 762 matching lines @@
 
 String LocalFrame::layerTreeAsText(unsigned flags) const
 {
     if (contentLayoutItem().isNull())
         return String();
 
     RefPtr<JSONObject> layerTree = contentLayoutItem().compositor()->layerTreeAsJSON(static_cast<LayerTreeFlags>(flags));
 
     if (flags & LayerTreeIncludesPaintInvalidations) {
         RefPtr<JSONArray> objectPaintInvalidations = m_view->trackedObjectPaintInvalidationsAsJSON();
-        if (objectPaintInvalidations) {
+        if (objectPaintInvalidations && objectPaintInvalidations->length()) {
             if (!layerTree)
                 layerTree = JSONObject::create();
             layerTree->setArray("objectPaintInvalidations", objectPaintInvalidations);
         }
     }
 
     return layerTree ? layerTree->toPrettyJSONString() : String();
 }
 
 bool LocalFrame::shouldThrottleRendering() const
@@ skipping 72 matching lines @@
         m_frame->client()->frameBlameContext()->Enter();
 }
 
 ScopedFrameBlamer::~ScopedFrameBlamer()
 {
     if (m_frame && m_frame->client() && m_frame->client()->frameBlameContext())
         m_frame->client()->frameBlameContext()->Leave();
 }
 
 } // namespace blink