tests for callbacks created and detached
improving tests according to Dominic's notes
fixing minor typos
changing tests according to clarifications from Dimitri Glazkov
improving tests according to Dominic's notes
Fix syntax errors in WebDriver client

Signed-off-by: AutomatedTester <dburns@mozilla.com>
Merge pull request #837 from sgrekhov/submission/unipro-custom-elements-8

Tests for Custom Elements created and detached callbacks
Don't probe IDBRequest.error if still pending