Replace the OVERRIDES list in PDFViewerApplication._readPreferences with a disablePreferences, in GENERIC builds, `AppOption instead

Rather than having a (somewhat) randomly choosen list of Preferences which `AppOptions` are allowed to override, it makes much more sense to simply add an AppOption to allow custom implementations to ignore Preferences altogether (it's also inline with the AppOption that allows the `ViewHistory` to be bypassed on load).

web/app.js

@@ -169,21 +169,14 @@ let PDFViewerApplication = {
    * @private
    */
   async _readPreferences() {
-    // A subset of the Preferences that `AppOptions`, for compatibility reasons,
-    // is allowed to override if the `AppOptions` values matches the ones below.
-    const OVERRIDES = {
-      disableFontFace: true,
-      disableRange: true,
-      disableStream: true,
-      textLayerMode: TextLayerMode.DISABLE,
-    };
-
+    if (AppOptions.get('disablePreferences') === true) {
+      // Give custom implementations of the default viewer a simpler way to
+      // opt-out of having the `Preferences` override existing `AppOptions`.
+      return;
+    }
     try {
       const prefs = await this.preferences.getAll();
-      for (let name in prefs) {
-        if ((name in OVERRIDES) && AppOptions.get(name) === OVERRIDES[name]) {
-          continue;
-        }
+      for (const name in prefs) {
         AppOptions.set(name, prefs[name]);
       }
     } catch (reason) { }

web/app_options.js

@@ -58,6 +58,9 @@ const defaultOptions = {
     value: false,
     kind: OptionKind.VIEWER,
   },
+  /**
+   * The `disablePreferences` is, conditionally, defined below.
+   */
   enablePrintAutoRotate: {
     /** @type {boolean} */
     value: false,
@@ -218,6 +221,11 @@ const defaultOptions = {
 };
 if (typeof PDFJSDev === 'undefined' ||
     PDFJSDev.test('!PRODUCTION || GENERIC')) {
+  defaultOptions.disablePreferences = {
+    /** @type {boolean} */
+    value: false,
+    kind: OptionKind.VIEWER,
+  };
   defaultOptions.locale = {
     /** @type {string} */
     value: (typeof navigator !== 'undefined' ? navigator.language : 'en-US'),