chore: Move addFont to DOM Utils (#8533)

Author: tykus160

lib/player.js

@@ -8612,33 +8612,11 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    *
    * @param {string} name
    * @param {string} url
+   * @return {!Promise<void>}
    * @export
    */
-  async addFont(name, url) {
-    if ('fonts' in document && 'FontFace' in window ) {
-      await document.fonts.ready;
-      if (!('entries' in document.fonts)) {
-        return;
-      }
-      const fontFaceSetIteratorToArray = (target) => {
-        const iterable = target.entries();
-        const results = [];
-        let iterator = iterable.next();
-        while (iterator.done === false) {
-          results.push(iterator.value);
-          iterator = iterable.next();
-        }
-        return results;
-      };
-      for (const fontFace of fontFaceSetIteratorToArray(document.fonts)) {
-        if (fontFace.family == name && fontFace.display == 'swap') {
-          // Font already loaded.
-          return;
-        }
-      }
-      const fontFace = new FontFace(name, `url(${url})`, {display: 'swap'});
-      document.fonts.add(fontFace);
-    }
+  addFont(name, url) {
+    return shaka.util.Dom.addFont(name, url);
   }
 
   /**

lib/util/dom_utils.js

@@ -158,5 +158,41 @@ shaka.util.Dom = class {
       element.removeChild(element.firstChild);
     }
   }
+
+  /**
+   * Load a new font on the page. If the font was already loaded, it does
+   * nothing.
+   *
+   * @param {string} name
+   * @param {string} url
+   * @return {!Promise<void>}
+   */
+  static async addFont(name, url) {
+    if (!('fonts' in document && 'FontFace' in window)) {
+      return;
+    }
+    await document.fonts.ready;
+    if (!('entries' in document.fonts)) {
+      return;
+    }
+    const fontFaceSetIteratorToArray = (target) => {
+      const iterable = target.entries();
+      const results = [];
+      let iterator = iterable.next();
+      while (iterator.done === false) {
+        results.push(iterator.value);
+        iterator = iterable.next();
+      }
+      return results;
+    };
+    for (const fontFace of fontFaceSetIteratorToArray(document.fonts)) {
+      if (fontFace.family === name && fontFace.display === 'swap') {
+        // Font already loaded.
+        return;
+      }
+    }
+    const fontFace = new FontFace(name, `url(${url})`, {display: 'swap'});
+    document.fonts.add(fontFace);
+  }
 };