git: openjdk/jdk-sandbox: simpleserver: simple-server: Change Headers::of to return an empty instance. Use Headers::of in the implementation

[Chris Hegarty]

Changeset: 6393754d
Author:    Chris Hegarty <chris.hegarty at oracle.com>
Date:      2021-06-18 16:11:51 +0000
URL:       https://git.openjdk.java.net/jdk-sandbox/commit/6393754d0a0a3829e8c27629cc707e4f7b2bded5

simple-server: Change Headers::of to return an empty instance. Use Headers::of in the implementation

! src/jdk.httpserver/share/classes/com/sun/net/httpserver/Headers.java
! src/jdk.httpserver/share/classes/sun/net/httpserver/FileServerHandler.java
! test/jdk/com/sun/net/httpserver/HeadersTest.java
! test/jdk/com/sun/net/httpserver/simpleserver/FileServerHandlerTest.java