RFR: 8279009: CDS crashes when the source of an InstanceKlass is NULL

[Yumin Qi]

Please review
  When user combine -XX:ArchiveClassesAtExit and -XX:DumpLoadedClassList, vm will generate shared archive at exit mean while dump class list to a file, it will encounter null source when lambda form invoker holder classes are regenerated which have no source.  It failed to output the NULL source.
   The fix is simply add ing check if the source exists. 
   For unregistered classes loaded from shared space, they should be filtered out since the source are not recorded in shared space.

   Tests: tier2,tier2.tier3,tier4

Thanks
Yumin

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Commit messages:
 - 8279009: CDS crashes when the source of an InstanceKlass is NULL

Changes: https://git.openjdk.java.net/jdk/pull/7072/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7072&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279009
  Stats: 475 lines in 5 files changed: 462 ins; 6 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7072.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7072/head:pull/7072

PR: https://git.openjdk.java.net/jdk/pull/7072