Do a better job of finding a scrollable element.

common/modules/base.jsm

@@ -228,9 +228,14 @@ function properties(obj, prototypes, debugger_) {
                 // currently.
                 let filter = function filter(prop) {
                     try {
-                        return k in obj;
+                        return prop in obj;
+                    }
+                    catch (e) {
+                        util.reportError("Filtering properties for " +
+                                         String.quote(obj) + ", " +
+                                         "error checking presence of " +
+                                         String.quote(prop) + ": " + e);
                     }
-                    catch (e) {}
                     return false;
                 };
                 return array.uniq([k for (k in obj)].concat(

common/modules/buffer.jsm

@@ -1277,7 +1277,7 @@ var Buffer = Module("Buffer", {
      * The pattern used to search for a scrollable element when we have
      * no starting point.
      */
-    SCROLLABLE_SEARCH_SELECTOR: "div",
+    SCROLLABLE_SEARCH_SELECTOR: "html, body, div",
 
     PageInfo: Struct("PageInfo", "name", "title", "action")
                         .localize("title"),