Let synchronized painting generate correct paint invalidation rects

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 2674 matching lines @@
 
     // Do this unconditionally to ensure container chain is marked when compositing status of the layer changes.
     layer->markAncestorChainForNeedsRepaint();
 }
 
 void PaintLayer::markAncestorChainForNeedsRepaint()
 {
     // Need to access compositingState(). We've ensured correct flag setting when compositingState() changes.
     DisableCompositingQueryAsserts disabler;
 
-    if (compositingState() != NotComposited)
-        return;
-
     PaintLayer* layer = this;
     while (true) {
+        if (layer->compositingState() == PaintsIntoOwnBacking)
+            return;
+        if (CompositedLayerMapping* groupedMapping = layer->groupedMapping()) {
+            groupedMapping->owningLayer().setNeedsRepaint();
+            return;
+        }
+
         PaintLayer* container = layer->parent();
         if (!container) {
             LayoutObject* owner = layer->layoutObject()->frame()->ownerLayoutObject();
             if (!owner)
                 break;
             container = owner->enclosingLayer();
         }
         if (container->isSelfPaintingLayer() || container->hasSelfPaintingLayerDescendant()) {
             if (container->m_needsRepaint)
                 break;
             container->m_needsRepaint = true;
         }
-        if (container->compositingState() != NotComposited)
-            break;
         layer = container;
     }
 }
 
 void PaintLayer::clearNeedsRepaintRecursively()
 {
     for (PaintLayer* child = firstChild(); child; child = child->nextSibling())
         child->clearNeedsRepaintRecursively();
     m_needsRepaint = false;
 }
@@ skipping 20 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif