fix: Fix compiler error on static use of "this" (#4699)

An internal build system failed to compile v4.3.0 due to the use of
static "this". This change fixes it.

Unfortunately, we are already running the latest public compiler
release, so there is no way we could have caught this on GitHub.

lib/polyfill/patchedmediakeys_apple.js

@@ -27,38 +27,39 @@ goog.require('shaka.util.StringUtils');
 shaka.polyfill.PatchedMediaKeysApple = class {
   /**
    * Installs the polyfill if needed.
-   * @param {boolean} enableUninstall enables uninstalling the polyfill
+   * @param {boolean=} enableUninstall enables uninstalling the polyfill
    * @export
    */
   static install(enableUninstall = false) {
+    // Alias
+    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;
+
     if (!window.HTMLVideoElement || !window.WebKitMediaKeys) {
       // No HTML5 video or no prefixed EME.
       return;
     }
 
     if (enableUninstall) {
-      this.enableUninstall = true;
-      this.originalHTMLMediaElementPrototypeMediaKeys =
+      PatchedMediaKeysApple.enableUninstall = true;
+      PatchedMediaKeysApple.originalHTMLMediaElementPrototypeMediaKeys =
         /** @type {!Object} */ (
           Object.getOwnPropertyDescriptor(
               // eslint-disable-next-line no-restricted-syntax
               HTMLMediaElement.prototype, 'mediaKeys',
           )
         );
-      // eslint-disable-next-line no-restricted-syntax
-      this.originalHTMLMediaElementPrototypeSetMediaKeys = HTMLMediaElement
-          .prototype.setMediaKeys;
-      this.originalWindowMediaKeys = window.MediaKeys;
-      this.originalWindowMediaKeySystemAccess = window.MediaKeySystemAccess;
-      this.originalNavigatorRequestMediaKeySystemAccess = navigator
-          .requestMediaKeySystemAccess;
+      PatchedMediaKeysApple.originalHTMLMediaElementPrototypeSetMediaKeys =
+          // eslint-disable-next-line no-restricted-syntax
+          HTMLMediaElement.prototype.setMediaKeys;
+      PatchedMediaKeysApple.originalWindowMediaKeys = window.MediaKeys;
+      PatchedMediaKeysApple.originalWindowMediaKeySystemAccess =
+          window.MediaKeySystemAccess;
+      PatchedMediaKeysApple.originalNavigatorRequestMediaKeySystemAccess =
+          navigator.requestMediaKeySystemAccess;
     }
 
     shaka.log.info('Using Apple-prefixed EME');
 
-    // Alias
-    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;
-
     // Delete mediaKeys to work around strict mode compatibility issues.
     // eslint-disable-next-line no-restricted-syntax
     delete HTMLMediaElement.prototype['mediaKeys'];
@@ -83,32 +84,36 @@ shaka.polyfill.PatchedMediaKeysApple = class {
    * @export
    */
   static uninstall() {
-    if (!this.enableUninstall) {
+    // Alias
+    const PatchedMediaKeysApple = shaka.polyfill.PatchedMediaKeysApple;
+
+    if (!PatchedMediaKeysApple.enableUninstall) {
       return;
     }
 
     shaka.log.info('Un-installing Apple-prefixed EME');
 
-    this.enableUninstall = false;
+    PatchedMediaKeysApple.enableUninstall = false;
     Object.defineProperty(
         // eslint-disable-next-line no-restricted-syntax
         HTMLMediaElement.prototype,
         'mediaKeys',
-        this.originalHTMLMediaElementPrototypeMediaKeys,
+        PatchedMediaKeysApple.originalHTMLMediaElementPrototypeMediaKeys,
     );
     // eslint-disable-next-line no-restricted-syntax
-    HTMLMediaElement.prototype.setMediaKeys = this
-        .originalHTMLMediaElementPrototypeSetMediaKeys;
-    window.MediaKeys = this.originalWindowMediaKeys;
-    window.MediaKeySystemAccess = this.originalWindowMediaKeySystemAccess;
-    navigator.requestMediaKeySystemAccess = this
-        .originalNavigatorRequestMediaKeySystemAccess;
-
-    this.originalWindowMediaKeys = null;
-    this.originalWindowMediaKeySystemAccess = null;
-    this.originalHTMLMediaElementPrototypeSetMediaKeys = null;
-    this.originalNavigatorRequestMediaKeySystemAccess = null;
-    this.originalHTMLMediaElementPrototypeMediaKeys = null;
+    HTMLMediaElement.prototype.setMediaKeys =
+        PatchedMediaKeysApple.originalHTMLMediaElementPrototypeSetMediaKeys;
+    window.MediaKeys = PatchedMediaKeysApple.originalWindowMediaKeys;
+    window.MediaKeySystemAccess =
+        PatchedMediaKeysApple.originalWindowMediaKeySystemAccess;
+    navigator.requestMediaKeySystemAccess =
+        PatchedMediaKeysApple.originalNavigatorRequestMediaKeySystemAccess;
+
+    PatchedMediaKeysApple.originalWindowMediaKeys = null;
+    PatchedMediaKeysApple.originalWindowMediaKeySystemAccess = null;
+    PatchedMediaKeysApple.originalHTMLMediaElementPrototypeSetMediaKeys = null;
+    PatchedMediaKeysApple.originalNavigatorRequestMediaKeySystemAccess = null;
+    PatchedMediaKeysApple.originalHTMLMediaElementPrototypeMediaKeys = null;
 
     window.shakaMediaKeysPolyfill = false;
   }