RFR: 8284884: Replace polling with waiting in javax/swing/text/html/parser/Parser/8078268/bug8078268.java [v2]

[Alexey Ivanov]

> A quick fix for the `javax/swing/text/html/parser/Parser/8078268/bug8078268.java` which replaces `Thread.sleep` in a loop with `CountDownLatch.await`.
> 
> The code is shorter and clearer.
> 
> The test fails on the builds without the fix for [JDK-8078268](https://bugs.openjdk.java.net/browse/JDK-8078268). I ran it in the CI and it passes.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Simplify filename handling

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8252/files
  - new: https://git.openjdk.java.net/jdk/pull/8252/files/0609a11f..83d6301d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8252&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8252&range=00-01

  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8252.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8252/head:pull/8252

PR: https://git.openjdk.java.net/jdk/pull/8252