[jdk21u-dev] RFR: 8342075: HttpClient: improve HTTP/2 flow control checks [v2]

[Alexey Bakhtin]

> Please review the backport of JDK-8342075
> 
> Almost clean backport except for the import section of src/java.net.http/share/classes/jdk/internal/net/http/Http2Connection.java
> 
> Requires JDK-8317808 [1] as a prerequisite to fixing the hanging of the new tests.
> 
> Also, new tests require Http2TestExchange::getConnectionKey() method added by JDK-8335181 [2].
> 
> test/jdk/java/net/httpclient/lib/jdk/httpclient/test/lib/http2/Http2TestExchange.java, test/jdk/java/net/httpclient/lib/jdk/httpclient/test/lib/http2/Http2TestExchangeImpl.java and test/jdk/java/net/httpclient/lib/jdk/httpclient/test/lib/http2/Http2TestServerConnection.java test classes are updated to add  getConnectionKey() implementation
> 
> All jtreg tests for java.net.httpclient are passed
> 
> [1] - https://github.com/openjdk/jdk21u-dev/pull/1426
> [2] - https://github.com/openjdk/jdk/commit/720b44648bcff997278af92746f942b2425298a5#diff-c18c2a070038409f25c08e13c174a95f33840e2deddcc29f6d8306de572a618b

Alexey Bakhtin 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.

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Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/1428/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/1428/files/ec9d0ca6..ec9d0ca6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1428&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1428&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1428.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1428/head:pull/1428

PR: https://git.openjdk.org/jdk21u-dev/pull/1428