RFR: 8259631: Reapply pattern match instanceof use in HttpClientImpl

[Chris Hegarty]

On Tue, 12 Jan 2021 16:05:01 GMT, Aleksei Efimov <aefimov at openjdk.org> wrote:

> Hi,
> 
> The proposed change adds back [1] `instanceof` pattern match use to `HttpClientImpl` class. It was previously removed by [JDK-8258696](https://bugs.openjdk.java.net/browse/JDK-8258696) due to docs build failure.
> 
> Aleksei
> 
> [1] `git rollback be41468c --no-commit`

Marked as reviewed by chegar (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/2051