RFR: JMC-6367 - Improve Thread graph tooltip

[Alex Macdonald]

Hi,

The following webrev [0] addresses issue JMC-6367 [1], in which the thread
lane tooltips should display descriptive information (thread & lane names)
pertaining to the highlighted lane.

The information to be displayed in the tooltip had to be carried in the
Span object which is passed to the ChartToolTipProvider. There was an
unused String description argument in the QuantitySpanRenderer which fits
this need, and allows for the passing of the tooltip title from the
ThreadGraphLanes through the QuantitySpanRenderer to the
QuantitySpanRendering. This change was also mirrored in the SpanRenderer.
If the Span obj has a description when it hits the ChartToolTipProvider, a
title will be appended to the tooltip.

I've created an imgur album [2] to show some examples. Some images
illustrate the before and after of this patch when viewing tooltips for a
thread [3][4], and viewing a thread that corresponds to an active filter
(e.g., Java Latencies lane) [5][6].

Thoughts?

Cheers,

Alex

[0] http://cr.openjdk.java.net/~aptmac/JMC-6367/webrev.00/
[1] https://bugs.openjdk.java.net/browse/JMC-6367
[2] https://imgur.com/a/TOuq1ez
[3] https://imgur.com/ueAbwHz
[4] https://imgur.com/OOqYZ4I
[5] https://imgur.com/K7JCa66
[6] https://imgur.com/mPe3ah3