Various fixes to getClientBoundingRect()

* Fix queries involving stacking contexts
 * The code was double accumulating stacking context origins.
* Handle queries of inline elements.
 * The node addresses being compared were incorrect (CharacterData vs. Span)
* Handle ScriptQuery reflows correctly.
 * The layout task was skipping the compute absolute positions traversal, so failed before window.onload.

components/layout/block.rs

@@ -1914,7 +1914,7 @@ impl Flow for BlockFlow {
                                                             self.base
                                                                 .absolute_position_info
                                                                 .relative_containing_block_mode,
-                                                            CoordinateSystem::Parent)
+                                                            CoordinateSystem::Own)
                               .translate(stacking_context_position));
     }