Add offset contributed to sticky position box rect by location containers

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

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index fa4d1c1e25981cdc0e9ed8acd3e685f2caf5507a..9488b171adb53029c112ed886c8ab8d6dcdd328e 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -2238,14 +2238,21 @@ FloatQuad LayoutObject::localToAncestorQuad(
     const FloatQuad& localQuad,
     const LayoutBoxModelObject* ancestor,
     MapCoordinatesFlags mode) const {
+  return localToAncestorQuadWithoutTransforms(localQuad, ancestor,
+                                              mode | UseTransforms);
+}
+
+FloatQuad LayoutObject::localToAncestorQuadWithoutTransforms(

[Xianzhu, 2017/01/24 22:53:11]

I like the direction of the new code, but
  localAncestorQuadWithoutTransforms( ...  UseTransforms)
looks weird.

How about adding 
  mapLocalToAncestorQuadInternal() which contains line 2249-2258, and

... ::localToAncestorQuad(...) {
  return mapLocalToAncestorQuadInternal(  ... | UseTransforms);
}

... ::localToAncestorQuadWithoutTransforms(...) {
  DCHECK(!(mode & UseTransforms));
  return mapLocalToAncestorQuadInternal(...);
}

[flackr, 2017/01/25 13:23:24]

Done.

+    const FloatQuad& localQuad,
+    const LayoutBoxModelObject* ancestor,
+    MapCoordinatesFlags mode) const {
   // Track the point at the center of the quad's bounding box. As
   // mapLocalToAncestor() calls offsetFromContainer(), it will use that point
   // as the reference point to decide which column's transform to apply in
   // multiple-column blocks.
   TransformState transformState(TransformState::ApplyTransformDirection,
                                 localQuad.boundingBox().center(), localQuad);
-  mapLocalToAncestor(ancestor, transformState,
-                     mode | ApplyContainerFlip | UseTransforms);
+  mapLocalToAncestor(ancestor, transformState, mode | ApplyContainerFlip);
   transformState.flatten();
 
   return transformState.lastPlanarQuad();