RFR: JMC-4466 - Hide thread directly from Thread graph context menu

[Alex Macdonald]

Hi,

The following webrev [0] addresses issue JMC-4466 [1], in which the user
should be able to hide threads from the thread chart using context menu
actions.

This patch adds functionality to the context menu to hide threads from the
chart. Additionally, I thought there should be an option to restore the
chart to the current selection to "unhide" the threads, so I've also
included a menu item that does such that. I've included a GIF [2] to
demonstrate how the actions work (note the gif was made before I touched up
some of the strings, so some of the wording may be off).

The "hide thread" action is only enabled while there are threads that can
be hidden, and the "reset chart" option is only enabled while the chart has
been modified (i.e., has thread(s) hidden) [3][4]. I've also included
uitests that perform the new actions on the chart, and verify the results
based on the enablement values of the menu items.

Lastly, I've tested these tests and changes locally on my machine and using
Travis [5], but these are both Linux environments and it would be nice to
make sure there are no issues on Windows / Mac.

Thoughts?

Cheers,

Alex

[0] http://cr.openjdk.java.net/~aptmac/JMC-4466/webrev.00/
[1] https://bugs.openjdk.java.net/browse/JMC-4466
[2] https://imgur.com/BkeXkVX
[3] https://imgur.com/dhuTmkE
[4] https://imgur.com/W7NzOj7
[5] https://travis-ci.org/aptmac/jmc-qa/builds/516268811