Bug 823228 part 1. Make browser-test.js ignore indexed properties on the window when determining whether a test leaked properties onto the global. r=dao

testing/mochitest/browser-test.js

@@ -254,6 +254,13 @@ Tester.prototype = {
       }
 
       Object.keys(window).forEach(function (prop) {
+        if (parseInt(prop) == prop) {
+          // This is a string which when parsed as an integer and then
+          // stringified gives the original string.  As in, this is in fact a
+          // string representation of an integer, so an index into
+          // window.frames.  Skip those.
+          return;
+        }
         if (this._globalProperties.indexOf(prop) == -1) {
           this._globalProperties.push(prop);
           if (this._globalPropertyWhitelist.indexOf(prop) == -1)