RFR: 8262913: KlassFactory::create_from_stream should never return NULL [v3]

[Coleen Phillimore]

> ClassFileParser.create_instance_klass cannot return NULL without a pending exception, it's called by 
>        klassFactory::create_from_stream who also cannot return NULL without a pending exception, it's called by
>        SystemDictionary::parse_stream and SystemDictionary::resolve_from_stream who also cannot return NULL without a pending exception.
> 
> I removed the NULL checks on returns from these 4 functions and either replaced them with an assert, or in cases that already had an unconditional indirection from the return value, just removed the null checks.
> 
> I wrote a test case to cover the case of testing st->buffer() == NULL which returned NULL from SystemDictionary::resolve_from_stream to show that this code path is not used. ClassFileStream constructor will set buffer() to the u1* input argument if it doesn't point to anything and will get a ClassFormatError.
> 
> Tested with tier1-3.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Improve test, suggested by Ioi.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2892/files
  - new: https://git.openjdk.java.net/jdk/pull/2892/files/88166bea..a9459502

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2892&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2892&range=01-02

  Stats: 15 lines in 1 file changed: 0 ins; 8 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2892.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2892/head:pull/2892

PR: https://git.openjdk.java.net/jdk/pull/2892