Fixes B2G file open sequence.

web/viewer.js

@@ -2301,6 +2301,8 @@ window.addEventListener('afterprint', function afterPrint(evt) {
 //  var fileURL = activity.source.data.url;
 //
 //  var url = URL.createObjectURL(blob);
+//  // We need to delay opening until all HTML is loaded.
+//  PDFViewerApplication.animationStartedPromise.then(function () {
 //    PDFViewerApplication.open({url : url, originalUrl: fileURL});
 //
 //    var header = document.getElementById('header');
@@ -2308,4 +2310,5 @@ window.addEventListener('afterprint', function afterPrint(evt) {
 //      activity.postResult('close');
 //    });
 //  });
+//});
 //#endif