Stop re-loading the Preferences in PDFViewerApplication.open, and remove the BasePreferences.reload method

Given that the various Preferences are currently, and have been for quite some time, only used when initializing `PDFViewerApplication` re-loading them when a new PDF file is opened in the viewer is essentially a no-op.

Furthermore, with the only usage of `BasePreferences.reload` now gone, the value of that method seems questionable at best. In the event that the functionality is actually needed again, similar to the `ViewHistory`, it'd probably make more sense to simply replace `PDFViewerApplication.preferences` with a new `BasePreferences` instance instead (using e.g. `DefaultExternalServices.createPreferences`).

Author: Snuffleupagus

web/app.js

@@ -635,8 +635,6 @@ let PDFViewerApplication = {
     if (this.pdfLoadingTask) {
       // We need to destroy already opened document.
       return this.close().then(() => {
-        // Reload the preferences if a document was previously opened.
-        this.preferences.reload();
         // ... and repeat the open() call.
         return this.open(file, args);
       });

web/preferences.js

@@ -99,21 +99,6 @@ class BasePreferences {
     });
   }
 
-  /**
-   * Replace the current preference values with the ones from storage.
-   * @return {Promise} A promise that is resolved when the preference values
-   *                   have been updated.
-   */
-  reload() {
-    return this._initializedPromise.then(() => {
-      return this._readFromStorage(this.defaults);
-    }).then((prefObj) => {
-      if (prefObj) {
-        this.prefs = prefObj;
-      }
-    });
-  }
-
   /**
    * Set the value of a preference.
    * @param {string} name The name of the preference that should be changed.