RFR: 8316383: NullPointerException in AbstractSAXParser after JDK-8306632 [v2]

[Joe Wang]

> Fix a NPE. The DTD patch (JDK-8306632) moved initialization to factories, for example, for SAXParser, the SecurityManagers are created in the SAXParserFactory impl and passed on to instances of SAXParsers. The (deprecated) XMLReaderFactory however, instantiates SAXParsers directly, thus without initializing the SecurityManagers. This patch checks the condition and creates them if they have not already been constructed.
> 
> Test: XML tests passed.

Joe Wang has updated the pull request incrementally with one additional commit since the last revision:

  fix indentation

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15828/files
  - new: https://git.openjdk.org/jdk/pull/15828/files/5c414425..711d5e24

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15828&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15828&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15828.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15828/head:pull/15828

PR: https://git.openjdk.org/jdk/pull/15828