Add option enableXfa to the viewer

extensions/chromium/preferences_schema.json

@@ -159,6 +159,10 @@
       "type": "boolean",
       "default": false
     },
+    "enableXfa": {
+      "type": "boolean",
+      "default": false
+    },
     "historyUpdateUrl": {
       "type": "boolean",
       "default": false

web/app.js

@@ -1555,7 +1555,7 @@ const PDFViewerApplication = {
       // Note: `isPureXfa === true` implies that `enableXfa = true` was set.
       !pdfDocument.isPureXfa
     ) {
-      console.warn("Warning: XFA is not supported");
+      console.warn("Warning: XFA is not enabled");
       this.fallback(UNSUPPORTED_FEATURES.forms);
     } else if (
       (info.IsAcroFormPresent || info.IsXFAPresent) &&

web/app_options.js

@@ -206,7 +206,7 @@ const defaultOptions = {
   enableXfa: {
     /** @type {boolean} */
     value: false,
-    kind: OptionKind.API,
+    kind: OptionKind.API + OptionKind.PREFERENCE,
   },
   fontExtraProperties: {
     /** @type {boolean} */