RFR: 8357714: AudioClip.play crash on macOS when loading resource from jar [v2]

[Johan Vos]

> After JDK-8287822 (https://bugs.openjdk.org/browse/JDK-8287822), mpeg file content is no longer played via GSTPlatform but via OSXPlatform. 
> We need to correctly handle data in case the source is a file inside a jar, in which case CJavaInputStreamCallbacks is used.
> 
> The 2 changes I made are:
> 1. Use ConnectionHolder instead of Locator for CJavaInputStreamCallbacks in case a jar resource is used.
> 2. In case of random access datasource, use readBlock instead of readNextBlock in AVMediaPlayer

Johan Vos has updated the pull request incrementally with one additional commit since the last revision:

  Process reviewer comments
  Add null checks
  Fix errors in position and length calculations

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1839/files
  - new: https://git.openjdk.org/jfx/pull/1839/files/b1459d09..e99a8504

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1839&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1839&range=00-01

  Stats: 19 lines in 2 files changed: 8 ins; 4 del; 7 mod
  Patch: https://git.openjdk.org/jfx/pull/1839.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1839/head:pull/1839

PR: https://git.openjdk.org/jfx/pull/1839