[css-grid] Fix behavior of positioned items without specific dimensions

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

Index: third_party/WebKit/Source/core/layout/LayoutGrid.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
index 9b70c14246c0977c6e1645927061b89b3aec95f0..0ff518fe28a25c532e10310d9fda35e48d181872 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -1263,16 +1263,17 @@ void LayoutGrid::LayoutPositionedObjects(bool relayout_children,
 
     child->SetOverrideContainingBlockContentLogicalWidth(column_breadth);
     child->SetOverrideContainingBlockContentLogicalHeight(row_breadth);
-    child->SetExtraInlineOffset(column_offset);
-    child->SetExtraBlockOffset(row_offset);
 
-    if (child->Parent() == this) {
-      PaintLayer* child_layer = child->Layer();
-      child_layer->SetStaticInlinePosition(BorderStart() + column_offset);
-      child_layer->SetStaticBlockPosition(BorderBefore() + row_offset);
-    }
+    // Mark for layout as we're resetting the position before and we relay in
+    // generic layout logic for positioned items in order to get the offsets
+    // properly resolved.
+    child->SetNeedsLayout(LayoutInvalidationReason::kGridChanged,
+                          kMarkOnlyThis);
 
     LayoutPositionedObject(child, relayout_children, info);
+
+    child->SetLogicalLocation(LayoutPoint(child->LogicalLeft() + column_offset,
+                                          child->LogicalTop() + row_offset));
   }
 }
 
@@ -1364,11 +1365,8 @@ void LayoutGrid::OffsetAndBreadthForPositionedChild(
   breadth = std::max(end - start, LayoutUnit());
   offset = start;
 
-  if (is_for_columns && !StyleRef().IsLeftToRightDirection() &&
-      !child.StyleRef().HasStaticInlinePosition(
-          child.IsHorizontalWritingMode())) {
-    // If the child doesn't have a static inline position (i.e. "left" and/or
-    // "right" aren't "auto", we need to calculate the offset from the left
+  if (is_for_columns && !StyleRef().IsLeftToRightDirection()) {
+    // We always want to calculate the static position from the left
     // (even if we're in RTL).
     if (end_is_auto) {
       offset = LayoutUnit();