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 2675 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)
+    if (compositingState() == PaintsIntoOwnBacking)

[chrishtr, 2015/10/22 00:02:41]

Not squashing?

[Xianzhu, 2015/10/22 01:17:04]

We need to mark needsRepaint until real GraphicsLayers because we issue
CachedDisplayItemList according to the needsRepaint flag of the root layer of a
real GraphicsLayer.

[chrishtr, 2015/10/23 17:15:06]

Then you need to stop at squashing layers and mark the owningLayer of the CLM
which has the squashing layer as needsRepaint.

[Xianzhu, 2015/10/23 18:43:27]

I realized this too :) Fixed in the patch set 7.

         return;
 
     PaintLayer* layer = this;
     while (true) {
         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)
+        if (container->compositingState() == PaintsIntoOwnBacking)
             break;
         layer = container;
     }
 }
 
 void PaintLayer::clearNeedsRepaintRecursively()
 {
     for (PaintLayer* child = firstChild(); child; child = child->nextSibling())
         child->clearNeedsRepaintRecursively();
     m_needsRepaint = false;
@@ skipping 37 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif