Enable position:sticky for <thead> and <tr> elements

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. 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
@@ skipping 15 matching lines @@
 #include "core/layout/LayoutBoxModelObject.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLBodyElement.h"
 #include "core/layout/ImageQualityController.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/LayoutFlexibleBox.h"
 #include "core/layout/LayoutGeometryMap.h"
 #include "core/layout/LayoutInline.h"
+#include "core/layout/LayoutTableCell.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/paint/ObjectPaintInvalidator.h"
 #include "core/paint/PaintLayer.h"
 #include "core/style/ShadowList.h"
 #include "platform/LengthFunctions.h"
 #include "platform/geometry/TransformState.h"
 #include "platform/scroll/MainThreadScrollingReason.h"
 #include "wtf/PtrUtil.h"
@@ skipping 935 matching lines @@
   sticky_location -= container_border_offset;
   constraints.SetScrollContainerRelativeStickyBoxRect(
       FloatRect(scroll_container_relative_padding_box_rect.Location() +
                     ToFloatSize(sticky_location),
                 flipped_sticky_box_rect.size()));
 
   // To correctly compute the offsets, the constraints need to know about any
   // nested position:sticky elements between themselves and their
   // containingBlock, and between the containingBlock and their scrollAncestor.
   //
-  // The respective search ranges are [container, containingBlock) and
+  // The respective search ranges are [locationContainer, containingBlock) and
   // [containingBlock, scrollAncestor).
+
+  // Table cells are a special case; Blink ignores them for locationContainer()
+  // purposes, but their sticky offset does affect descendant sticky objects.
+  // TODO(smcgruer): Remove cell override once Blink supports the correct
+  // locationContainer for CSS 3.
+  LayoutObject* location_container_for_sticky =
+      IsTableCell() ? ToLayoutTableCell(this)->Row() : location_container;
+
   constraints.SetNearestStickyBoxShiftingStickyBox(
-      FindFirstStickyBetween(location_container, containing_block));
+      FindFirstStickyBetween(location_container_for_sticky, containing_block));
+
   // We cannot use |scrollAncestor| here as it disregards the root
   // ancestorOverflowLayer(), which we should include.
   constraints.SetNearestStickyBoxShiftingContainingBlock(FindFirstStickyBetween(
       containing_block, &Layer()->AncestorOverflowLayer()->GetLayoutObject()));
 
   // We skip the right or top sticky offset if there is not enough space to
   // honor both the left/right or top/bottom offsets.
   LayoutUnit horizontal_offsets =
       MinimumValueForLength(Style()->Right(),
                             LayoutUnit(constraining_size.Width())) +
@@ skipping 474 matching lines @@
   if (root_element_style->HasBackground())
     return false;
 
   if (GetNode() != GetDocument().FirstBodyElement())
     return false;
 
   return true;
 }
 
 }  // namespace blink