[8u] RFR: 8150204: (fs) Enhance java/nio/file/Files/probeContentType/Basic.java debugging output

[Alex Kashchenko]

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Hi,

Please review the backport of JDK-8150204 to 8u:

Bug: https://bugs.openjdk.java.net/browse/JDK-8150204

Related thread: 
https://mail.openjdk.java.net/pipermail/jdk8u-dev/2020-June/012055.html

9 change: https://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/e4af8119eba4

8u webrev: https://cr.openjdk.java.net/~akasko/jdk8u/8150204/webrev.00/

This change is a prerequisite to JDK-8146215, only test code is changed, 
patch requires adjustments for 8u because it includes changes from 
JDK-8129632 that is not in 8u, macOS-specific part is omitted.

-- 
-Alex