RFR: 8335536: Fix assertion failure in IdealGraphPrinter when append is true [v2]

[Christian Hagedorn]

On Wed, 3 Jul 2024 06:34:31 GMT, Qizheng Xing <qxing at openjdk.org> wrote:

>> When `IdealGraphPrinter` is created with `append` set to true, it does not write the head element to the file in its constructor. But in the destructor, it always writes the tail element to the file no matter `append` is true or not, which causes an assertion failure in `xmlStream::pop_tag`.
>> 
>> This issue can be reproduced by calling `igv_append` directly, or by calling `Compile::igv_print_method_to_file` with `append` set to true.
>> 
>> This patch fixes the issue.
>
> Qizheng Xing has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comments for `IdealGraphPrinter::update_compiled_method`.

Looks good to me, too.

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19986#pullrequestreview-2155718358