XFA - Move the fake HTML representation of XFA from the worker to the main thread

- the only goal of this patch is to be able to get synchronously the fake html when printing from firefox:
    - in order to print we need to inject some html in beforeprint callback but we cannot block in waiting for all the pages.
  - from a memory point of view: it doesn't change anything since the fake HTML is deleted in the worker;
  - this way we don't break any assumptions.

src/core/worker.js

@@ -187,13 +187,13 @@ class WorkerMessageHandler {
         await pdfManager.ensureDoc("checkFirstPage");
       }
 
-      const [numPages, fingerprint, isPureXfa] = await Promise.all([
+      const [numPages, fingerprint, htmlForXfa] = await Promise.all([
         pdfManager.ensureDoc("numPages"),
         pdfManager.ensureDoc("fingerprint"),
-        pdfManager.ensureDoc("isPureXfa"),
+        pdfManager.ensureDoc("htmlForXfa"),
       ]);
 
-      if (isPureXfa) {
+      if (htmlForXfa) {
         const task = new WorkerTask("loadXfaFonts");
         startWorkerTask(task);
         await pdfManager
@@ -203,7 +203,7 @@ class WorkerMessageHandler {
           })
           .then(() => finishWorkerTask(task));
       }
-      return { numPages, fingerprint, isPureXfa };
+      return { numPages, fingerprint, htmlForXfa };
     }
 
     function getPdfManager(data, evaluatorOptions, enableXfa) {
@@ -501,12 +501,6 @@ class WorkerMessageHandler {
       });
     });
 
-    handler.on("GetPageXfa", function wphSetupGetXfa({ pageIndex }) {
-      return pdfManager.getPage(pageIndex).then(function (page) {
-        return pdfManager.ensure(page, "xfaData");
-      });
-    });
-
     handler.on("GetOutline", function wphSetupGetOutline(data) {
       return pdfManager.ensureCatalog("documentOutline");
     });