RFR: 8246348: Crash in libpango on Ubuntu 20.04 with some unicode chars

[Phil Race]

On Thu, 11 Jun 2020 19:20:05 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> I did a quick test, and setting `start = str` fixes the spurious assertions and intermittent crash.
>
> I should add that this is without any attempt to filter out `0` chars. Both `UnicodeTextTest` and  `UnicodeTextTest2`
> run correctly with no crashes and no assertions when I comment out the (ineffective) loop checking for 0 and set `start
> = str` leaving everything else as you have it in the current PR. Loading https://gluonhq.com/ in WebView works, too.

I agree. the text array is now the subset for the run, so effectively run.getStart() should be zero,
so there should be no need for that call. This probably looks OK when there is one run not otherwise.

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PR: https://git.openjdk.java.net/jfx/pull/249