RFR: 8264999: GeneralPath.lineTo() to itself produces jagged lines [v4]

[Jeremy]

> Previously when you drew a line that moved exactly (+0, +0) with a miter stroke the Stroker class acted like a horizontal miter was appropriate. Now we abort instead, so no miter is applied.
> 
> The new unit test tests the original steps plus several variations.
> 
> I'm a little nervous about this change because it looks like someone previously considered this exact condition and implemented a different behavior. I don't think I understand the original rationale.

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

  JDK-8264999: GeneralPath.lineTo() to itself produces jagged lines
  
  Revising failing (commented out) scenarios.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/8943/files
  - new: https://git.openjdk.org/jdk/pull/8943/files/f14b5598..328eb462

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8943&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8943&range=02-03

  Stats: 18 lines in 1 file changed: 9 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/8943.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/8943/head:pull/8943

PR: https://git.openjdk.org/jdk/pull/8943