Detect a change in border that affects a positioned object's height or position

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 412 matching lines @@
     bool heightChanged = (previousHeight != newHeight);
     if (heightChanged)
         relayoutChildren = true;
 
     layoutPositionedObjects(relayoutChildren || isDocumentElement(), oldLeft != logicalLeft() ? ForcedLayoutAfterContainingBlockMoved : DefaultLayout);
 
     // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
     computeOverflow(oldClientAfterEdge);
 
     m_descendantsWithFloatsMarkedForLayout = false;
+    m_heightAvailableToChildrenChanged = false;

[mstensho (USE GERRIT), 2016/02/17 10:19:42]

So we'll only reset this flag for LayoutBlockFlow, and not for other LayoutBlock
types, such as LayoutTable and LayoutFlexibleBox.

m_widthAvailableToChildrenChanged has the same problem, though.

updateLogicalWidthAndColumnWidth(), which *may* call
widthAvailableToChildrenHasChanged(), which resets the flag.
updateLogicalWidthAndColumnWidth() is only called from LayoutBlockFlow and
LayoutFlexibleBox, but the flag is never reset if oldWidth != logicalWidth() in
updateLogicalWidthAndColumnWidth().

We should probably clean up this, but that's for a different CL. Could you add a
TODO here, though?

     return true;
 }
 
 void LayoutBlockFlow::addLowestFloatFromChildren(LayoutBlockFlow* block)
 {
     // TODO(robhogan): Make createsNewFormattingContext an ASSERT.
     if (!block || !block->containsFloats() || block->createsNewFormattingContext())
         return;
 
     FloatingObject* floatingObject = block->m_floatingObjects->lowestFloatingObject();
@@ skipping 2415 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = LayoutUnit((style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height());
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink