[devtools] qunit: use new async testing APIs http://qunitjs.com/cookbook/#asynchronous-callbacks QUnit keeps track of all the assert.async() objects created inside the test functions and expects all done() functions to be called. Failure to do so will result in the test being failed. Unlike .start and .stop which were internal APIs, assert.async() is stricter and fails tests if assert methods are used *after* all done() functions are called (see "test callback execution order"). Related to #5533333.

[devtools] qunit: use new assert APIs test functions now accept an "assert" argument which exposes QUnit's assert methods: assert.{expect,equal,deepEqual,ok} Related to #5533333.

[devtools] qunit: stop using global variables test -> QUnit.test module -> QUnit.module Related to #5533333.

[devtools] qunit: update to 1.18.0 (closes #5533333) * the logging API has changed (register callbacks instead of setting attributes on the QUnit object) * the logging callbacks all have a single "details" object argument * the "main" div was renamed to "qunit-fixture" (this change is responsible for all the churn in our own JS test files) * QUnit can now build the DOM elements it needs for reporting from a single "qunit" div

[devtools] qunit: stop using deprecated assert functions equals -> equal same -> deepEqual Related to #5533333.

[devtools] qunit: remove useless window.close() Modern browsers don't allow it anymore. Related to #5533333.