Fix a regression when position:static with absolute child changed to relative

Source/core/layout/LayoutObject.cpp

Index: Source/core/layout/LayoutObject.cpp
diff --git a/Source/core/layout/LayoutObject.cpp b/Source/core/layout/LayoutObject.cpp
index 39912284a41dacf2f68f32faac07fca4172e674a..f9044c996db85fc62b0b941f1b49f7117dd1c6a8 100644
--- a/Source/core/layout/LayoutObject.cpp
+++ b/Source/core/layout/LayoutObject.cpp
@@ -865,6 +865,31 @@ LayoutBlock* LayoutObject::containerForFixedPosition(const LayoutBoxModelObject*
     return toLayoutBlock(ancestor);
 }
 
+LayoutBlock* LayoutObject::containerForAbsolutePosition() const
+{
+    LayoutObject* o = parent();
+    while (o) {
+        if (o->style()->position() != StaticPosition && (!o->isInline() || o->isReplaced()))
+            break;
+
+        if (o->canContainFixedPositionObjects())
+            break;
+
+        o = o->parent();
+    }
+
+    if (o && !o->isLayoutBlock())
+        o = o->containingBlock();
+
+    while (o && o->isAnonymousBlock())
+        o = o->containingBlock();
+
+    if (!o || !o->isLayoutBlock())
+        return nullptr; // This can still happen in case of an orphaned tree
+
+    return toLayoutBlock(o);
+}
+
 LayoutBlock* LayoutObject::containingBlock() const
 {
     LayoutObject* o = parent();
@@ -872,23 +897,9 @@ LayoutBlock* LayoutObject::containingBlock() const
         o = toLayoutScrollbarPart(this)->layoutObjectOwningScrollbar();
     if (!isTextOrSVGChild() && m_style->position() == FixedPosition)
         return containerForFixedPosition();
-    if (!isTextOrSVGChild() && m_style->position() == AbsolutePosition) {
-        while (o) {
-            if (o->style()->position() != StaticPosition && (!o->isInline() || o->isReplaced()))
-                break;
-
-            if (o->canContainFixedPositionObjects())
-                break;
-
-            o = o->parent();
-        }
-
-        if (o && !o->isLayoutBlock())
-            o = o->containingBlock();
-
-        while (o && o->isAnonymousBlock())
-            o = o->containingBlock();
-    } else if (isColumnSpanAll()) {
+    if (!isTextOrSVGChild() && m_style->position() == AbsolutePosition)

[mstensho (USE GERRIT), 2015/07/06 09:46:24]

Kind of silly to call isTextOrSVGChild() all day long, although not expensive.
You've just made it possible to move the check to an outer scope.

if (!isTextOrSVGChild()) {
    if (fixedpos)
        return blah;
    if (abspos)
        return fish;
}

[kojii, 2015/07/07 08:40:38]

Done.

+        return containerForAbsolutePosition();

[mstensho (USE GERRIT), 2015/07/06 09:46:24]

containingBlockForAbsolutePosition() is a better name. container() locates a
containing block for abspos differently from what containingBlock() does.

[kojii, 2015/07/07 08:40:38]

Done.

+    if (isColumnSpanAll()) {
         o = spannerPlaceholder()->containingBlock();
     } else {
         while (o && ((o->isInline() && !o->isReplaced()) || !o->isLayoutBlock()))