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diff --git a/toolkit/components/formautofill/shared/LabelUtils.sys.mjs b/toolkit/components/formautofill/shared/LabelUtils.sys.mjs
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+++ b/toolkit/components/formautofill/shared/LabelUtils.sys.mjs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This is a utility object to work with HTML labels in web pages,
+ * including finding label elements and label text extraction.
+ */
+export const LabelUtils = {
+  // The tag name list is from Chromium except for "STYLE":
+  // eslint-disable-next-line max-len
+  // https://cs.chromium.org/chromium/src/components/autofill/content/renderer/form_autofill_util.cc?l=216&rcl=d33a171b7c308a64dc3372fac3da2179c63b419e
+  EXCLUDED_TAGS: ["SCRIPT", "NOSCRIPT", "OPTION", "STYLE"],
+
+  // A map object, whose keys are the id's of form fields and each value is an
+  // array consisting of label elements correponding to the id.
+  // @type {Map<string, array>}
+  _mappedLabels: null,
+
+  // An array consisting of label elements whose correponding form field doesn't
+  // have an id attribute.
+  // @type {Array<[HTMLLabelElement, HTMLElement]>}
+  _unmappedLabelControls: null,
+
+  // A weak map consisting of label element and extracted strings pairs.
+  // @type {WeakMap<HTMLLabelElement, array>}
+  _labelStrings: null,
+
+  /**
+   * Extract all strings of an element's children to an array.
+   * "element.textContent" is a string which is merged of all children nodes,
+   * and this function provides an array of the strings contains in an element.
+   *
+   * @param  {object} element
+   *         A DOM element to be extracted.
+   * @returns {Array}
+   *          All strings in an element.
+   */
+  extractLabelStrings(element) {
+    if (this._labelStrings.has(element)) {
+      return this._labelStrings.get(element);
+    }
+    let strings = [];
+    let _extractLabelStrings = el => {
+      if (this.EXCLUDED_TAGS.includes(el.tagName)) {
+        return;
+      }
+
+      if (el.nodeType == el.TEXT_NODE || !el.childNodes.length) {
+        let trimmedText = el.textContent.trim();
+        if (trimmedText) {
+          strings.push(trimmedText);
+        }
+        return;
+      }
+
+      for (let node of el.childNodes) {
+        let nodeType = node.nodeType;
+        if (nodeType != node.ELEMENT_NODE && nodeType != node.TEXT_NODE) {
+          continue;
+        }
+        _extractLabelStrings(node);
+      }
+    };
+    _extractLabelStrings(element);
+    this._labelStrings.set(element, strings);
+    return strings;
+  },
+
+  generateLabelMap(doc) {
+    this._mappedLabels = new Map();
+    this._unmappedLabelControls = [];
+    this._labelStrings = new WeakMap();
+
+    for (let label of doc.querySelectorAll("label")) {
+      let id = label.htmlFor;
+      let control;
+      if (!id) {
+        control = label.control;
+        if (!control) {
+          continue;
+        }
+        id = control.id;
+      }
+      if (id) {
+        let labels = this._mappedLabels.get(id);
+        if (labels) {
+          labels.push(label);
+        } else {
+          this._mappedLabels.set(id, [label]);
+        }
+      } else {
+        // control must be non-empty here
+        this._unmappedLabelControls.push({ label, control });
+      }
+    }
+  },
+
+  clearLabelMap() {
+    this._mappedLabels = null;
+    this._unmappedLabelControls = null;
+    this._labelStrings = null;
+  },
+
+  findLabelElements(element) {
+    if (!this._mappedLabels) {
+      this.generateLabelMap(element.ownerDocument);
+    }
+
+    let id = element.id;
+    if (!id) {
+      return this._unmappedLabelControls
+        .filter(lc => lc.control == element)
+        .map(lc => lc.label);
+    }
+    return this._mappedLabels.get(id) || [];
+  },
+};
+
+export default LabelUtils;