[OpenJDK 2D-Dev] RFR: 8263894: Convert defaultPrinter and printers fields to local variables

[Alexey Ivanov]

`PrintServiceLookupProvider` has `defaultPrinter` and `printers` fields but they are used only in `getDefaultPrintService()` and `refreshServices()` correspondingly. Thus these two fields can be converted to local variables in the corresponding methods.

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Commit messages:
 - 8263894: Convert defaultPrinter and printers fields to local variables

Changes: https://git.openjdk.java.net/jdk/pull/3095/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3095&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263894
  Stats: 5 lines in 1 file changed: 0 ins; 2 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3095.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3095/head:pull/3095

PR: https://git.openjdk.java.net/jdk/pull/3095