RFR: 8277983: Remove unused fields from s.n.w.p.j.JarURLConnection

[Сергей Цыпанов]

There are some fields that are unused in current implementation of `JarURLConnection`:
- debug
- jarFileURL
- permission
- jarFileURLConnection (inherited one can be used)

They can be safely removed reducing object footprint. Before:

sun.net.www.protocol.jar.JarURLConnection object internals:
 OFFSET  SIZE                        TYPE DESCRIPTION                               VALUE
      0    12                             (object header)                           N/A
     12     4                         int URLConnection.connectTimeout              N/A
     16     8                        long URLConnection.ifModifiedSince             N/A
     24     4                         int URLConnection.readTimeout                 N/A
     28     1                     boolean URLConnection.doInput                     N/A
     29     1                     boolean URLConnection.doOutput                    N/A
     30     1                     boolean URLConnection.allowUserInteraction        N/A
     31     1                     boolean URLConnection.useCaches                   N/A
     32     1                     boolean URLConnection.connected                   N/A
     33     3                             (alignment/padding gap)                  
     36     4                java.net.URL URLConnection.url                         N/A
     40     4   sun.net.www.MessageHeader URLConnection.requests                    N/A
     44     4                java.net.URL JarURLConnection.jarFileURL               N/A
     48     4            java.lang.String JarURLConnection.entryName                N/A
     52     4      java.net.URLConnection JarURLConnection.jarFileURLConnection     N/A
     56     4                java.net.URL JarURLConnection.jarFileURL               N/A
     60     4    java.security.Permission JarURLConnection.permission               N/A
     64     4      java.net.URLConnection JarURLConnection.jarFileURLConnection     N/A
     68     4            java.lang.String JarURLConnection.entryName                N/A
     72     4      java.util.jar.JarEntry JarURLConnection.jarEntry                 N/A
     76     4       java.util.jar.JarFile JarURLConnection.jarFile                  N/A
     80     4            java.lang.String JarURLConnection.contentType              N/A
     84     4                             (loss due to the next object alignment)
Instance size: 88 bytes
Space losses: 3 bytes internal + 4 bytes external = 7 bytes total

After:

sun.net.www.protocol.jar.JarURLConnection object internals:
 OFFSET  SIZE                        TYPE DESCRIPTION                               VALUE
      0    12                             (object header)                           N/A
     12     4                         int URLConnection.connectTimeout              N/A
     16     8                        long URLConnection.ifModifiedSince             N/A
     24     4                         int URLConnection.readTimeout                 N/A
     28     1                     boolean URLConnection.doInput                     N/A
     29     1                     boolean URLConnection.doOutput                    N/A
     30     1                     boolean URLConnection.allowUserInteraction        N/A
     31     1                     boolean URLConnection.useCaches                   N/A
     32     1                     boolean URLConnection.connected                   N/A
     33     3                             (alignment/padding gap)                  
     36     4                java.net.URL URLConnection.url                         N/A
     40     4   sun.net.www.MessageHeader URLConnection.requests                    N/A
     44     4                java.net.URL JarURLConnection.jarFileURL               N/A
     48     4            java.lang.String JarURLConnection.entryName                N/A
     52     4      java.net.URLConnection JarURLConnection.jarFileURLConnection     N/A
     56     4      java.util.jar.JarEntry JarURLConnection.jarEntry                 N/A
     60     4       java.util.jar.JarFile JarURLConnection.jarFile                  N/A
     64     4            java.lang.String JarURLConnection.contentType              N/A
     68     4                             (loss due to the next object alignment)
Instance size: 72 bytes
Space losses: 3 bytes internal + 4 bytes external = 7 bytes total

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

Commit messages:
 - Remove entryName
 - 8277983: Remove unused fields from s.n.w.p.j.JarURLConnection

Changes: https://git.openjdk.java.net/jdk/pull/6649/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6649&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277983
  Stats: 35 lines in 1 file changed: 4 ins; 24 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6649.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6649/head:pull/6649

PR: https://git.openjdk.java.net/jdk/pull/6649