[SPInvalidation] Fix PrePaintTreeWalk for multicol spanner

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

Index: third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
diff --git a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
index 88219c07e0ad3c123b77e27d5f373ca3dda82d4d..c69e82f09c0496fd79a4cad78ad75a45308300a3 100644
--- a/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
+++ b/third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h
@@ -22,9 +22,9 @@ class ObjectPaintProperties;
 // 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
@@ -50,24 +50,26 @@ struct PaintPropertyTreeBuilderContext {
     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.