[SPInvalidation] Fix PrePaintTreeWalk for multicol spanner

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PaintPropertyTreeBuilder_h
 #define PaintPropertyTreeBuilder_h
 
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/EffectPaintPropertyNode.h"
 #include "platform/graphics/paint/ScrollPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class FrameView;
 class LayoutObject;
 class ObjectPaintProperties;
 
 // The context for PaintPropertyTreeBuilder.
 // It's responsible for bookkeeping tree state in other order, for example, the most recent
 // position container seen.
 struct PaintPropertyTreeBuilderContext {
-  // State that propagates on the containing block chain (and so is adjusted
-  // when an absolute or fixed position object is encountered).
-  struct ContainingBlockContext {
+  // State that propagates on the container chain (and so is adjusted when an

[chrishtr, 2016/10/06 16:22:32]

What do mean by container? Calling container()? parent()?

[Xianzhu, 2016/10/06 16:47:48]

container().

Previous "containing block" was not accurate because it might be also a
relative-position LayoutInline (as the container of an absolute-position
object).

[chrishtr, 2016/10/06 16:54:21]

container() is actually containing block, as defined by CSS.

https://chromium.googlesource.com/chromium/src/+/master/third_party/WebKit/So...
(see reference to container())

Walter plans to rename those methods soon to be less confusing. In the meantime
I think it would be better to change this back to ContainingBlockContext.

[Xianzhu, 2016/10/06 17:33:00]

I should have read Walter's doc more thoroughly. It's great to make clear of the
concepts.

Reverted the changes about ContainingBlockContext.

+  // absolute or fixed position object is encountered).
+  struct ContainerContext {
     // The combination of a transform and paint offset describes a linear space.
     // When a layout object recur to its children, the main context is expected to refer
     // the object's border box, then the callee will derive its own border box by translating
     // the space with its own layout location.
     const TransformPaintPropertyNode* transform = nullptr;
     LayoutPoint paintOffset;
     // Whether newly created children should flatten their inherited transform
     // (equivalently, draw into the plane of their parent). Should generally
     // be updated whenever |transform| is; flattening only needs to happen
     // to immediate children.
     bool shouldFlattenInheritedTransform = false;
     // Rendering context for 3D sorting. See
     // TransformPaintPropertyNode::renderingContextID.
     unsigned renderingContextID = 0;
     // The clip node describes the accumulated raster clip for the current subtree.
     // Note that the computed raster region in canvas space for a clip node is independent from
     // the transform and paint offset above. Also the actual raster region may be affected
     // by layerization and occlusion tracking.
     const ClipPaintPropertyNode* clip = nullptr;
     // The scroll node contains information for scrolling such as the parent scroll space, the
     // extent that can be scrolled, etc. Because scroll nodes reference a scroll offset
     // transform, scroll nodes should be updated if the transform tree changes.
     ScrollPaintPropertyNode* scroll = nullptr;
   };
 
-  ContainingBlockContext current;
+  ContainerContext current;
 
-  // Separate context for out-of-flow positioned and fixed positioned elements are needed
-  // because they don't use DOM parent as their containing block.
-  // These additional contexts normally pass through untouched, and are only copied from
-  // the main context when the current element serves as the containing block of corresponding
-  // positioned descendants.
-  // Overflow clips are also inherited by containing block tree instead of DOM tree, thus they
-  // are included in the additional context too.
-  ContainingBlockContext absolutePosition;
+  // Separate context for out-of-flow positioned and fixed positioned elements
+  // are needed because they don't use DOM parent as their container.
+  // These additional contexts normally pass through untouched, and are only
+  // copied from the main context when the current element serves as the
+  // container of corresponding positioned descendants.
+  // Overflow clips are also inherited by container tree instead of DOM tree,
+  // thus they are included in the additional context too.
+  ContainerContext absolutePosition;
   const LayoutObject* containerForAbsolutePosition = nullptr;
 
-  ContainingBlockContext fixedPosition;
+  ContainerContext fixedPosition;
 
   // The effect hierarchy is applied by the stacking context tree. It is guaranteed that every
   // DOM descendant is also a stacking context descendant. Therefore, we don't need extra
   // bookkeeping for effect nodes and can generate the effect tree from a DOM-order traversal.
   const EffectPaintPropertyNode* currentEffect = nullptr;
+
+  bool isUnderMultiColumnSpanner = false;
 };
 
 // Creates paint property tree nodes for special things in the layout tree.
 // Special things include but not limit to: overflow clip, transform, fixed-pos, animation,
 // mask, filter, ... etc.
 // It expects to be invoked for each layout tree node in DOM order during InPrePaint phase.
 class PaintPropertyTreeBuilder {
  public:
   PaintPropertyTreeBuilderContext setupInitialContext();
   void buildTreeNodes(FrameView&, PaintPropertyTreeBuilderContext&);
@@ skipping 29 matching lines @@
   static void updateScrollAndScrollTranslation(
       const LayoutObject&,
       PaintPropertyTreeBuilderContext&);
   static void updateOutOfFlowContext(const LayoutObject&,
                                      PaintPropertyTreeBuilderContext&);
 };
 
 }  // namespace blink
 
 #endif  // PaintPropertyTreeBuilder_h