RFR: JDK-8297449: Update JInternalFrame Metal Border code [v2]

[Harshitha Onkar]

On Mon, 28 Nov 2022 23:07:12 GMT, SWinxy <duke at openjdk.org> wrote:

>> Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   review changes
>
> src/java.desktop/share/classes/javax/swing/plaf/metal/MetalBorders.java line 267:
> 
>> 265:             }
>> 266: 
>> 267:             AffineTransform at = null;
> 
> Because we'd no longer be causing a `ClassCastException` from casting this to be a `Graphics2D` object, later down on line 311, if the `Graphics` object isn't a G2D type, then it will throw an NPE. I fear matrices, so I have no idea what the value of `getScaleX()` would be otherwise--replace it with zero if null?

@SWinxy Thanks for catching it. That's right, but the scale factor cannot be zero, it should probably be handled similar to `stkWidth` if **'at is null'** (at is null when g is not an instance of Graphics2D). I'll need to check the scale value to be used in this context.

Something like below. 
 `at != null ? at.getScaleX() : 1;`

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PR: https://git.openjdk.org/jdk/pull/11305