Handle nested position:sticky elements correctly (compositor)

cc/layers/layer_sticky_position_constraint.h

Index: cc/layers/layer_sticky_position_constraint.h
diff --git a/cc/layers/layer_sticky_position_constraint.h b/cc/layers/layer_sticky_position_constraint.h
index 3f43bc7751ab614b2c12b25c18d73a71cd308012..55e832ae6182c9cc94e4b520122aebc8531d5d05 100644
--- a/cc/layers/layer_sticky_position_constraint.h
+++ b/cc/layers/layer_sticky_position_constraint.h
@@ -11,6 +11,8 @@
 
 namespace cc {
 
+class Layer;
+
 struct CC_EXPORT LayerStickyPositionConstraint {
   LayerStickyPositionConstraint();
   LayerStickyPositionConstraint(const LayerStickyPositionConstraint& other);
@@ -44,6 +46,14 @@ struct CC_EXPORT LayerStickyPositionConstraint {
   // block boundary.
   gfx::Rect scroll_container_relative_containing_block_rect;
 
+  Layer* nearest_layer_shifting_sticky_box;
+  Layer* nearest_layer_shifting_containing_block;
+
+  gfx::Vector2dF total_sticky_box_sticky_offset;
+  gfx::Vector2dF total_containing_block_sticky_offset;
+
+  gfx::Vector2dF local_sticky_offset;
+
   bool operator==(const LayerStickyPositionConstraint&) const;
   bool operator!=(const LayerStickyPositionConstraint&) const;
 };