[jdk8u-ri] RFR: 8071507: (ref) Clear phantom reference as soft and weak references do [v2]

[Andrew John Hughes]

On Thu, 21 Apr 2022 16:05:25 GMT, Poonam Bajaj <poonam at openjdk.org> wrote:

>> These changes backport the following fixes to jdk8u-ri:
>> - 8071507: (ref) Clear phantom reference as soft and weak references do
>> - 8143847: Remove REF_CLEANER reference category
>> 
>> With these changes, phantom references are automatically cleared by the garbage collector as soft and weak references.
>
> Poonam Bajaj has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Corrected documentation in package.html

Is there a reason for backporting two changes in one PR? I see this was done in 8u42 as well. It makes it harder to review than necessary, notably where the two change the same code in `referenceProcessor.cpp`.

Also, SKARA does not appear to be picking this up as a backport, as the "Backport <commit>" style was not used (https://wiki.openjdk.org/display/SKARA/Backports). Ideally it would refer to the changeset in 8u42, [ad6cdea5ae385623afa86251a8278c9c5274f4c1](https://git.openjdk.java.net/jdk8u-ri/commit/ad6cdea5ae385623afa86251a8278c9c5274f4c1), but it may have to be one of the three original changesets from jdk

In the code itself, three files are missing copyright header changes where they are newer than the current version: `referenceProcessor.hpp`, `referenceProcessor.cpp" and `referenceType.hpp`.  8143847 bumps all of these to 2016 and this change should do the same. The other files already have a newer copyright year than in 8143847.

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PR: https://git.openjdk.org/jdk8u-ri/pull/4