Rename isTreatedAsOrStackingContext to isStacked

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

Index: third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h b/third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h
index 15a42259b6a14da477a716952d36812365143d2f..9193cbc968e8369d3ccc215fed52ebd90b23ce94 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayerStackingNode.h
@@ -64,7 +64,7 @@ class LayoutBoxModelObject;
 // Stacking contexts are the basis for the CSS painting algorithm. The paint
 // order is determined by walking stacking contexts (or elements treated like a
 // stacking context like positioned objects or floats) in an order defined by
-// ‘z-index’. This walk is interleaved with content that is not a stacking.
+// ‘z-index’. This walk is interleaved with content that is not a stacking
 // context. See CSS 2.1 appendix E for the actual algorithm
 // http://www.w3.org/TR/CSS21/zindex.html
 // See also PaintLayerPainter (in particular paintLayerContents) for
@@ -105,8 +105,8 @@ public:
     bool hasPositiveZOrderList() const { return posZOrderList() && posZOrderList()->size(); }
     bool hasNegativeZOrderList() const { return negZOrderList() && negZOrderList()->size(); }
 
-    bool isTreatedAsOrStackingContext() const { return m_isTreatedAsOrStackingContext; }
-    void updateIsTreatedAsStackingContext();
+    bool isStacked() const { return m_isStacked; }
+    void updateIsStacked();
 
     void updateStackingNodesAfterStyleChange(const ComputedStyle* oldStyle);
 
@@ -119,6 +119,18 @@ public:
     void setLayerListMutationAllowed(bool flag) { m_layerListMutationAllowed = flag; }
 #endif
 
+    // Stacking contexts and positioned elements[1] are stacked (sorted in negZOrderList
+    // and posZOrderList) in their enclosing stacking contexts.
+    //
+    // [1] According to CSS2.1, Appendix E.2.8 (https://www.w3.org/TR/CSS21/zindex.html),
+    // positioned elements with 'z-index: auto' are "treated as if it created a new
+    // stacking context" and z-ordered together with other elements with 'z-index: 0'.
+    // The difference of them from normal stacking contexts is that they don't determine
+    // the stacking of the elements underneath them.
+    // (Note: There are also other elements treated as stacking context during painting,
+    // but not managed in stacks. See ObjectPainter::paintAllPhasesAtomically().)

[pdr., 2016/03/16 02:22:53]

Optional, may want to add a link to the markdown too:
https://chromium.googlesource.com/chromium/src.git/+/master/third_party/WebKi...

[Xianzhu, 2016/03/16 18:10:24]

Done.

+    static bool shouldStackObject(const LayoutObject& object) { return object.styleRef().isStackingContext() || object.isPositioned(); }
+
 private:
     friend class PaintLayerStackingNodeIterator;
     friend class PaintLayerStackingNodeReverseIterator;
@@ -147,8 +159,6 @@ private:
     void setStackingParent(PaintLayerStackingNode* stackingParent) { m_stackingParent = stackingParent; }
 #endif
 
-    bool shouldBeTreatedAsOrStackingContext() const { return layoutObject()->style()->isTreatedAsOrStackingContext(); }
-
     bool isDirtyStackingContext() const { return m_zOrderListsDirty && isStackingContext(); }
 
     PaintLayerCompositor* compositor() const;
@@ -158,7 +168,7 @@ private:
     PaintLayer* m_layer;
 
     // m_posZOrderList holds a sorted list of all the descendant nodes within
-    // that have z-indices of 0 or greater (auto will count as 0).
+    // that have z-indices of 0 (or is treated as 0 for positioned objects) or greater.
     // m_negZOrderList holds descendants within our stacking context with
     // negative z-indices.
     OwnPtr<Vector<PaintLayerStackingNode*>> m_posZOrderList;
@@ -169,11 +179,10 @@ private:
     // have z-order lists.
     unsigned m_zOrderListsDirty : 1;
 
-    // This attribute caches whether the element was a stacking context or
-    // was treated like a stacking context, so that we can do comparison against
+    // This attribute caches whether the element was stacked, so that we can do comparison against
     // it during style change (styleDidChange in particular), as we have lost
     // the previous style information.
-    unsigned m_isTreatedAsOrStackingContext: 1;
+    unsigned m_isStacked: 1;
 
 #if ENABLE(ASSERT)
     unsigned m_layerListMutationAllowed : 1;