RFR: 8273678 TableAccessibility and TableRowAccessibility miss autorelease

[Artem Semenov]

The TableAccessibility obj-c class should call [autorelease] on an object it allocates (see: [TableRowAccessibility alloc] and [ColumnAccessibility alloc]). 

The TableRowAccessibility obj-c class should not call [retain] on an allocated object (see: [CellAccessibility alloc]). 

"You own any object you create", see: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html

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Commit messages:
 - 8273678 TableAccessibility and TableRowAccessibility miss autorelease

Changes: https://git.openjdk.java.net/jdk/pull/6020/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6020&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273678
  Stats: 231 lines in 5 files changed: 136 ins; 78 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6020.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6020/head:pull/6020

PR: https://git.openjdk.java.net/jdk/pull/6020