Embedded PDF viewers should not be changing their parent page's title.

web/viewer.js

@@ -434,6 +434,10 @@ var PDFViewerApplication = {
   },
 
   setTitle: function pdfViewSetTitle(title) {
+    if (this.isViewerEmbedded) {
+      // Embedded PDF viewers should not be changing their parent page's title.
+      return;
+    }
     document.title = title;
 //#if B2G
 //  document.getElementById('activityTitle').textContent = title;