Loading URL's in to TestWebView is racy

[Chris Coulson]

There are lots of this pattern in tests:

webView.url = <some_url>;
verify(webView.waitForLoadSucceeded());

TestWebView tracks successful loads with qtest_loadsSucceededCount. waitForLoadSucceeded() increments another counter (qtest_expectedLoadsSucceededCount) and waits until they both match.

As these counts get out of sync, we have another function - clearLoadEventCounters() which resets all of these. A solution to some test failures is to place calls to this in various places.

It might be better to add a new call to TestWebView (loadUrlAndWait, or something like that), which:
- Stops pending loads and waits for them to stop.
- Loads WebView.url
- Waits for the load to succeed.

It would probably be easier to make this more reliable and race free.