RFR: JDK-8268088: Clarify Method::clear_jmethod_ids() related comments in ClassLoaderData::~ClassLoaderData() [v2]

[Jiangli Zhou]

On Mon, 7 Jun 2021 15:50:50 GMT, Jiangli Zhou <jiangli at openjdk.org> wrote:

>> This PR clarifies Method::clear_jmethod_ids() related comments in ClassLoaderData::~ClassLoaderData(). It adds more explanations on why Method::clear_jmethod_ids only sets the jmethod_ids to NULL without releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
>
> Jiangli Zhou has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove whitespace.
>  - Updated based on Evgeny's comments.

Thanks for the review!

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PR: https://git.openjdk.java.net/jdk/pull/4383