RFR: JDK-8289238: Refactoring changes to PassFailJFrame Test Framework

[Harshitha Onkar]

Currently PassFailJFrame.positionTestFrame() and PassFailJFrame.addTestFrame() take Frame as input parameter, this has been changed to Window.

Refactored the above method names to reflect the functionality & input parameter type -
addTestWindow(), positionTestWindow()

Additionally added test fail reason to `forceFail()` to avoid NPE.

Benefits of the change -

- Since Window is a parent class, this would allow the test frame to be a Window/Frame/Dialog and not be restricted to a Frame.
- Code reusability - no need to have separate methods to manage Frame and Window
- Additionally it would allow proper clean-up of window and its container subclasses which are added to the PassFailJFrame.

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Commit messages:
 - PassFailJFrame refactoring changes

Changes: https://git.openjdk.org/jdk/pull/9300/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9300&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289238
  Stats: 41 lines in 8 files changed: 3 ins; 3 del; 35 mod
  Patch: https://git.openjdk.org/jdk/pull/9300.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9300/head:pull/9300

PR: https://git.openjdk.org/jdk/pull/9300