LayoutTests: fast/js/resources/js-test-pre.js - shouldBeEqualToString fails on "

LayoutTests: fast/js/resources/js-test-pre.js - shouldBeEqualToString fails on "
https://bugs.webkit.org/show_bug.cgi?id=86931

Implementations of shouldBeEqualToString() function were not correctly escaping
double quote ('"') characters. Switch to using JSON.stringify() which does
correct escaping, and updated one test that couldn't previously use the function.

Reviewed by Ojan Vafai.

* fast/js/resources/js-test-pre.js:
(shouldBeEqualToString):
* fast/js/resources/standalone-pre.js:
(shouldBeEqualToString):
* storage/indexeddb/cursor-advance-expected.txt:
* storage/indexeddb/resources/cursor-advance.js:
(runTest):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117806 268f45cc-cd09-0410-ab3c-d52691b4dbfc