Ensure positioned descendants are invalidated if needed

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 357 matching lines @@
     // If the style has unloaded images, want to notify the ResourceLoadPriorityOptimizer so that
     // network priorities can be set.
     Vector<ImageResource*> images;
     appendImagesFromStyle(images, *newStyle);
     if (images.isEmpty())
         ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->removeRenderObject(this);
     else
         ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->addRenderObject(this);
 }
 
-void RenderBlock::invalidateTreeIfNeeded(const PaintInvalidationState& paintInvalidationState)
+void RenderBlock::invalidatePaintOfSubtreesIfNeeded(const PaintInvalidationState& childPaintInvalidationState)
 {
-    // Note, we don't want to early out here using shouldCheckForInvalidationAfterLayout as
-    // we have to make sure we go through any positioned objects as they won't be seen in

[dsinclair, 2014/10/16 13:32:37]

Since we no longer override invalidateTreeIfNeeded, the RenderObject version
will early out if !shouldCheckForInvalidationAfterLayout() is true. Which means,
won't we now miss the updating of positioned objects?

[Xianzhu, 2014/10/16 17:37:14]

The previous logic walks 1 extra level into the positioned descendants for
RenderBlock which has no paint invalidation flag set.

With this change:
- If the RenderBlock did change location, we'll force invalidation checking for
descendants (non-positioned as well as positioned).
- Otherwise the positioned descendants should be only checked paint invalidation
if the RenderBlock has been laid out. In the case, we have set
mayNeedPaintInvalidation for the positioned descendants in
RenderBlock::layoutPositionedObjects().

-    // the normal tree walk.
-
-    RenderBox::invalidateTreeIfNeeded(paintInvalidationState);
+    RenderBox::invalidatePaintOfSubtreesIfNeeded(childPaintInvalidationState);
 
     // Take care of positioned objects. This is required as PaintInvalidationState keeps a single clip rect.
     if (TrackedRendererListHashSet* positionedObjects = this->positionedObjects()) {
         TrackedRendererListHashSet::iterator end = positionedObjects->end();
-        bool establishesNewPaintInvalidationContainer = isPaintInvalidationContainer();
-        const RenderLayerModelObject& newPaintInvalidationContainer = *adjustCompositedContainerForSpecialAncestors(establishesNewPaintInvalidationContainer ? this : &paintInvalidationState.paintInvalidationContainer());
-        PaintInvalidationState childPaintInvalidationState(paintInvalidationState, *this, newPaintInvalidationContainer);
         for (TrackedRendererListHashSet::iterator it = positionedObjects->begin(); it != end; ++it) {
             RenderBox* box = *it;
 
             // One of the renderers we're skipping over here may be the child's paint invalidation container,
             // so we can't pass our own paint invalidation container along.
             const RenderLayerModelObject& paintInvalidationContainerForChild = *box->containerForPaintInvalidation();
 
             // If it's a new paint invalidation container, we won't have properly accumulated the offset into the
             // PaintInvalidationState.
             // FIXME: Teach PaintInvalidationState to handle this case. crbug.com/371485
-            if (&paintInvalidationContainerForChild != newPaintInvalidationContainer) {
+            if (paintInvalidationContainerForChild != childPaintInvalidationState.paintInvalidationContainer()) {
                 ForceHorriblySlowRectMapping slowRectMapping(&childPaintInvalidationState);
                 PaintInvalidationState disabledPaintInvalidationState(childPaintInvalidationState, *this, paintInvalidationContainerForChild);
                 box->invalidateTreeIfNeeded(disabledPaintInvalidationState);
                 continue;
             }
 
             // If the positioned renderer is absolutely positioned and it is inside
             // a relatively positioned inline element, we need to account for
             // the inline elements position in PaintInvalidationState.
             if (box->style()->position() == AbsolutePosition) {
@@ skipping 3943 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace blink