Correct for enclosing layers scroll position in sticky_data->main_thread_offset

cc/trees/property_tree_builder.cc

Index: cc/trees/property_tree_builder.cc
diff --git a/cc/trees/property_tree_builder.cc b/cc/trees/property_tree_builder.cc
index 375051ac04087affe87b921490b34eb9c0e83702..74b2c232cd776defa1e267e70d8fdbe7453f1eff 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -759,10 +759,19 @@ bool AddTransformNodeIfNeeded(
             .AddNodeAffectedByOuterViewportBoundsDelta(node->id);
       }
     }
-    sticky_data->main_thread_offset =
-        layer->position().OffsetFromOrigin() -
-        sticky_data->constraints.parent_relative_sticky_box_offset
-            .OffsetFromOrigin();
+
+    // The sticky box offset calculated in CompositedLayerMapping must be
+    // adjusted for the enclosing layer's scroll position.
+    gfx::Point sticky_box_offset(
+        sticky_data->constraints.parent_relative_sticky_box_offset);
+    if (Parent(layer)->id() != scroll_ancestor->owning_layer_id) {
+      sticky_box_offset -= gfx::ScrollOffsetToFlooredVector2d(
+          data_for_children->property_trees->scroll_tree.current_scroll_offset(
+              scroll_ancestor->owning_layer_id));
+    }
+
+    sticky_data->main_thread_offset = layer->position().OffsetFromOrigin() -
+                                      sticky_box_offset.OffsetFromOrigin();
   }
 
   node->needs_local_transform_update = true;