Bug 1147487 - don't try to reader-ize non-HTML documents, r=margaret,jaws

--HG--
extra : rebase_source : 107eb010f3c7967e038b7a0b4895425e4e3e7312

toolkit/components/reader/ReaderMode.jsm

@@ -68,8 +68,12 @@ this.ReaderMode = {
    * @return boolean Whether or not we should show the reader mode button.
    */
   isProbablyReaderable: function(doc) {
-    let uri = Services.io.newURI(doc.location.href, null, null);
+    // Only care about 'real' HTML documents:
+    if (doc.mozSyntheticDocument || !(doc instanceof doc.defaultView.HTMLDocument)) {
+      return false;
+    }
 
+    let uri = Services.io.newURI(doc.location.href, null, null);
     if (!this._shouldCheckUri(uri)) {
       return false;
     }