Don't schedule an animation during compositing dirty-bit setting unless needed.

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2770 matching lines @@
 
     ScrollView::paintOverhangAreas(context, horizontalOverhangArea, verticalOverhangArea, dirtyRect);
 }
 
 void FrameView::updateLayoutAndStyleForPainting()
 {
     // Updating layout can run script, which can tear down the FrameView.
     RefPtr<FrameView> protector(this);
 
     updateLayoutAndStyleIfNeededRecursive();
-    if (RenderView* view = renderView())
+    if (RenderView* view = renderView()) {
+        ASSERT(!view->needsLayout());
         view->compositor()->updateCompositingLayers();
+
+        // FIXME: we should not have any dirty bits left at this point. Unfortunately, this is not yet the case because
+        // the code in updateCompositingLayers sometimes creates new dirty bits when updating direct compositing reasons.
+        view->compositor()->scheduleAnimationIfNeeded();

[abarth-chromium, 2014/03/19 18:26:11]

Would you be willing to file a bug on this topic?  If there are unresolved dirty
bits, that means we'll put up a bad frame, right?

[chrishtr, 2014/03/19 18:31:14]

Done.

+    }
 }
 
 void FrameView::updateLayoutAndStyleIfNeededRecursive()
 {
     // We have to crawl our entire tree looking for any FrameViews that need
     // layout and make sure they are up to date.
     // Mac actually tests for intersection with the dirty region and tries not to
     // update layout for frames that are outside the dirty region.  Not only does this seem
     // pointless (since those frames will have set a zero timer to layout anyway), but
     // it is also incorrect, since if two frames overlap, the first could be excluded from the dirty
@@ skipping 413 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore