Keep track of fixed positioning in accessibility tree.

third_party/WebKit/Source/modules/accessibility/AXSpinButton.h

Index: third_party/WebKit/Source/modules/accessibility/AXSpinButton.h
diff --git a/third_party/WebKit/Source/modules/accessibility/AXSpinButton.h b/third_party/WebKit/Source/modules/accessibility/AXSpinButton.h
index 85fcad89f78040f4cdf25f2ee2feafd84aa8ce6a..93b41133e1b750bcdc7e61fa894039f5bc1f9787 100644
--- a/third_party/WebKit/Source/modules/accessibility/AXSpinButton.h
+++ b/third_party/WebKit/Source/modules/accessibility/AXSpinButton.h
@@ -75,7 +75,8 @@ class AXSpinButtonPart final : public AXMockObject {
   bool IsSpinButtonPart() const override { return true; }
   void GetRelativeBounds(AXObject** out_container,
                          FloatRect& out_bounds_in_container,
-                         SkMatrix44& out_container_transform) const override;
+                         SkMatrix44& out_container_transform,
+                         bool& out_is_fixed_positioned) const override;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXSpinButton, IsNativeSpinButton());