[Editor] Unselect correctly removed editors

- After undoing a deletion of several editors, they appeared to be selected (they had a red border)
when in fact they were not, consequently, this patch aims to remove the selectedEditor class when
an editor is removed;
- Add a test with some ink editors.

test/integration/test_utils.js

@@ -73,3 +73,19 @@ function getComputedStyleSelector(id) {
   return `getComputedStyle(${getQuerySelector(id)})`;
 }
 exports.getComputedStyleSelector = getComputedStyleSelector;
+
+const editorPrefix = "#pdfjs_internal_editor_";
+exports.editorPrefix = editorPrefix;
+
+function getSelectedEditors(page) {
+  return page.evaluate(prefix => {
+    const elements = document.querySelectorAll(".selectedEditor");
+    const results = [];
+    for (const { id } of elements) {
+      results.push(parseInt(id.slice(prefix.length)));
+    }
+    results.sort();
+    return results;
+  }, editorPrefix.slice(1));
+}
+exports.getSelectedEditors = getSelectedEditors;