RFR: 8295324: JavaFX: Blank pages when printing [v3]

[eduardsdv]

> This fixes a race condition between application and 'Print Job Thread' threads when printing.
> 
> The race condition occurs when application thread calls `endJob()`, which in effect sets the `jobDone` flag to true,
> and when the 'Print Job Thread' thread was in the `synchronized` block in `waitForNextPage()` at that time.
> The 'Print Job Thread' thread checks `jobDone` flag after exiting the `synchronized` block and, if it is true, skips the last page.
> 
> In this fix, not only the `jobDone` is checked, but also that there is no other page to be printed.
> It was also needed to introduce a new flag 'jobCanceled', to skip the page if the printing was canceled by 'cancelJob()'.

eduardsdv has updated the pull request incrementally with two additional commits since the last revision:

 - 8295324: Fix skipping of pages when printing
   
   This occurs in print(Graphics, PageFormat, int) if the 'jobDone' flag
   was previously set by the 'endJob()' method.
 - 8295324: Adjust the J2DPrinterJobTest
   
   The test now also checks for the second race condition around 'jobDone'
   flag, which is in the print(Graphics, PageFormat, int) method.

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/916/files
  - new: https://git.openjdk.org/jfx/pull/916/files/fdec73d8..acd4825b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=916&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=916&range=01-02

  Stats: 85 lines in 2 files changed: 47 ins; 18 del; 20 mod
  Patch: https://git.openjdk.org/jfx/pull/916.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/916/head:pull/916

PR: https://git.openjdk.org/jfx/pull/916