RFR: 8253005: Add `@throws IOException` in javadoc for `HttpEchange.sendResponseHeaders` [v8]

[Patrick Concannon]

> Hi,
> 
> Could someone please review my fix for JDK-8253005: 'Add `@throws IOException` in javadoc for `HttpEchange.sendResponseHeaders`' ?
> 
> The method `HttpEchange.sendResponseHeaders` throws an `IOException` but is unspecified in its javadoc. This fix adds an `@throws IOException` to its specification and a description of the conditions under which the exception is thrown.
> 
> Kind regards,
> Patrick

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 11 additional commits since the last revision:

 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - 8252304: Added read to TestHandler to ensure requestBody consumed before closing exchange
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - 8253005: Added test to verify `IOException` thrown when headers already sent
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - Merge remote-tracking branch 'origin/master' into JDK-8253005
 - ... and 1 more: https://git.openjdk.java.net/jdk/compare/8ed2c117...e3f6ddbb

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1014/files
  - new: https://git.openjdk.java.net/jdk/pull/1014/files/814a7fd0..e3f6ddbb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1014&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1014&range=06-07

  Stats: 213 lines in 21 files changed: 166 ins; 19 del; 28 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1014.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1014/head:pull/1014

PR: https://git.openjdk.java.net/jdk/pull/1014