RFR: 8252304: Seed an HttpRequest.Builder from an existing HttpRequest [v3]

[Patrick Concannon]

> Hi,
> 
> Could someone please review our code for JDK-8252304: 'Seed an HttpRequest.Builder from an existing HttpRequest'?
> 
> This RFR proposes a new factory method for creating a new `HttpRequest` builder from an existing `HttpRequest`.
> This method can be used to build a new request equivalent to the given request, but with different attributes. For instance, it will allow the user to take an existing request and add or change a particular header, provide a new `URI`, etc.
> 
> 
> Kind regards,
> Patrick & Chris

Patrick Concannon has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - 8252304: Removed catch block from newBuilder(HttpRequest)
 - 8252304: assertBodyPublisherEqual added to test; added comment to newBuilder
 - Merge remote-tracking branch 'origin/master' into JDK-8252304
 - Merge remote-tracking branch 'origin/master' into JDK-8252304
 - Merge remote-tracking branch 'origin/master' into JDK-8252304
 - 8252304: Seed an HttpRequest.Builder from an existing HttpRequest

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1059/files
  - new: https://git.openjdk.java.net/jdk/pull/1059/files/060aafae..cabc0e70

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1059&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1059&range=01-02

  Stats: 182 lines in 11 files changed: 104 ins; 27 del; 51 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1059.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1059/head:pull/1059

PR: https://git.openjdk.java.net/jdk/pull/1059