RFR: 5734: Overflow in stacktrace tooltips on Mac

[Guru Hb]

[Mac os] stacktrace tooltip view lines used to overflow with second line clipped. 
Solution : Stacktrace contains two list element, by adding span to list element with 'nowarp=true' solves the problem as similarly done in ChartToolTipProvider.

<img width="955" alt="jmc-5734" src="https://user-images.githubusercontent.com/1955702/98459172-30227700-21be-11eb-8fa9-3513feba4614.png">

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Commit messages:
 - Merge branch '5734' of https://github.com/guruhb/jmc into 5734
 - 5734: Overflow in stacktrace tooltips on Mac
 - 5734: Overflow in stacktrace tooltips on Mac

Changes: https://git.openjdk.java.net/jmc/pull/157/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=157&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-5734
  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jmc/pull/157.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/157/head:pull/157

PR: https://git.openjdk.java.net/jmc/pull/157