[RFR] [openjfx12] 8213135: HTMLEditorTest.checkStyleProperty fails intermittently

[Arunprasad Rajkumar]

Hi Kevin/Murali,

Please review the patch for the following bug,

Root cause: 
WebView load workers's state change notification received for the default page of HTMLEditor and not for the html doc which loaded using setHtmlText. The erroneous notification caused assertion check on invalid html document. The problem is not just specific to `checkStyleProperty`, it is applicable for all of the tests present in HTMLEditorTest. 

Proposed solution: 
Cancel the default page load before attaching the loader state change observer.

Webrev: http://cr.openjdk.java.net/~arajkumar/8213135/webrev/ 

Following changes are made in the webrev,
1. Cancel the default page load of HTMLEditor before loading test page (for all tests in HTMLEditorTest).
2. Moved common test object initialisation to separate method using junit @Before.
3. Added helper method in Util.java to wait for the latch to complete.

Regards,
Arun