Keep track of fixed positioning in accessibility tree.

third_party/WebKit/Source/modules/accessibility/AXObject.cpp

Index: third_party/WebKit/Source/modules/accessibility/AXObject.cpp
diff --git a/third_party/WebKit/Source/modules/accessibility/AXObject.cpp b/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
index f7145d1222ce32544ce1452749a5150af2eccd15..6825f6c4c3971660fae8d7f3028f6fa3ee86b8c8 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXObject.cpp
@@ -1490,10 +1490,12 @@ void AXObject::SetScrollOffset(const IntPoint& offset) const {
 
 void AXObject::GetRelativeBounds(AXObject** out_container,
                                  FloatRect& out_bounds_in_container,
-                                 SkMatrix44& out_container_transform) const {
+                                 SkMatrix44& out_container_transform,
+                                 bool& out_is_fixed_positioned) const {
   *out_container = nullptr;
   out_bounds_in_container = FloatRect();
   out_container_transform.setIdentity();
+  out_is_fixed_positioned = false;
 
   // First check if it has explicit bounds, for example if this element is tied
   // to a canvas path. When explicit coordinates are provided, the ID of the
@@ -1519,6 +1521,15 @@ void AXObject::GetRelativeBounds(AXObject** out_container,
     return;
   }
 
+  // When the object is fixed-positioned, we just need to return our
+  // absolute coordinates and indicate that the position is fixed.
+  if (layout_object->IsFixedPositioned()) {
+    out_bounds_in_container = layout_object->AbsoluteBoundingBoxFloatRect();
+    *out_container = AxObjectCache().Root();
+    out_is_fixed_positioned = true;
+    return;
+  }
+
   // First compute the container. The container must be an ancestor in the
   // accessibility tree, and its LayoutObject must be an ancestor in the layout
   // tree. Get the first such ancestor that's either scrollable or has a paint
@@ -1527,11 +1538,11 @@ void AXObject::GetRelativeBounds(AXObject** out_container,
   LayoutObject* container_layout_object = nullptr;
   while (container) {
     container_layout_object = container->GetLayoutObject();
-    if (container_layout_object &&
-        container_layout_object->IsBoxModelObject() &&
+    if (container_layout_object && container_layout_object->IsBox() &&
         layout_object->IsDescendantOf(container_layout_object)) {
       if (container->IsScrollableContainer() ||
-          container_layout_object->HasLayer())
+          container_layout_object->HasLayer() ||
+          container_layout_object->IsFixedPositioned())
         break;
     }
 
@@ -1569,11 +1580,12 @@ LayoutRect AXObject::GetBoundsInFrameCoordinates() const {
   AXObject* container = nullptr;
   FloatRect bounds;
   SkMatrix44 transform;
-  GetRelativeBounds(&container, bounds, transform);
+  bool is_fixed_positioned;
+  GetRelativeBounds(&container, bounds, transform, is_fixed_positioned);
   FloatRect computed_bounds(0, 0, bounds.Width(), bounds.Height());
   while (container && container != this) {
     computed_bounds.Move(bounds.X(), bounds.Y());
-    if (!container->IsWebArea()) {
+    if (!container->IsWebArea() && !is_fixed_positioned) {
       computed_bounds.Move(-container->GetScrollOffset().X(),
                            -container->GetScrollOffset().Y());
     }
@@ -1581,7 +1593,8 @@ LayoutRect AXObject::GetBoundsInFrameCoordinates() const {
       TransformationMatrix transformation_matrix(transform);
       transformation_matrix.MapRect(computed_bounds);
     }
-    container->GetRelativeBounds(&container, bounds, transform);
+    container->GetRelativeBounds(&container, bounds, transform,
+                                 is_fixed_positioned);
   }
   return LayoutRect(computed_bounds);
 }