RFR: 4668290: unclear spec for Polygon.bounds field [v4]

[SWinxy]

> New documentation replaces the `This value can be null.`:
> 
> When created, {@link #invalidate() invalidated}, or {@link #reset() reset},
> this becomes {@code null}. To get out of the null state,
> {@link #getBounds()} called with {@link #npoints} being greater than
> {@code 0} will transfer into a non-null {@link Rectangle}.
> 
> 
> I think I've got the reason for why it can be `null` correct, but you never know.
> 
> In javax.swing.text.html.Map, I've replaced setting the field to null with the equivalent #invalidate(). This may mean we can make the field private in the future.

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

  dash

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10417/files
  - new: https://git.openjdk.org/jdk/pull/10417/files/9b6f7d91..c62b8066

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10417&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10417&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10417.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10417/head:pull/10417

PR: https://git.openjdk.org/jdk/pull/10417