Schedule cursor update when DOM updates layout.

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1871 matching lines @@
         // View layout should not be re-entrant.
         ASSERT_NOT_REACHED();
         return;
     }
 
     if (HTMLFrameOwnerElement* owner = ownerElement())
         owner->document().updateLayout();
 
     updateRenderTreeIfNeeded();
 
+    if (LocalFrame* frame = this->frame())
+        frame->eventHandler().scheduleCursorUpdate();

[Rick Byers, 2015/02/12 00:07:13]

This is a good start.  I think this could trigger to aggressively though - eg.
if frameView->needsLayout is false then we probably don't want to schedule an
update.  The idea here is that we need to update the cursor only if layout
actually changed (not just if something thinks they need to check to see if
layout should be updated).

Digging down through this code, it looks like  FrameView::performPostLayoutTasks
(which gets invoked from the frameView->layout call below) is probably a better
place.

+
     if (!isActive())
         return;
 
     if (frameView->needsLayout())
         frameView->layout();
 
     if (lifecycle().state() < DocumentLifecycle::LayoutClean)
         lifecycle().advanceTo(DocumentLifecycle::LayoutClean);
 }
 
@@ skipping 3867 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif