Auto merge of #23171 - hundredeir:find_elem_elems, r=jdm

add webdriver command "Find elements from Element"

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/webdriver_handlers.rs

@@ -220,6 +220,28 @@ pub fn handle_find_element_element_css(
     reply.send(node_id).unwrap();
 }
 
+pub fn handle_find_element_elements_css(
+    documents: &Documents,
+    pipeline: PipelineId,
+    element_id: String,
+    selector: String,
+    reply: IpcSender<Result<Option<String>, ()>>,
+) {
+    let node_ids = find_node_by_unique_id(documents, pipeline, element_id)
+        .ok_or(())
+        .and_then(|node| {
+            node.query_selector_all(DOMString::from(selector))
+                .map_err(|_| ())
+        })
+        .map(|nodes| {
+            nodes
+                .iter()
+                .map(|x| Some(x.upcast::<Node>().unique_id()))
+                .collect()
+        });
+    reply.send(node_ids).unwrap();
+}
+
 pub fn handle_focus_element(
     documents: &Documents,
     pipeline: PipelineId,