RFR: 8172169: Re-examine String field optionality

[Claes Redestad]

Hi,

hash_offset and coder_offset are set up to be optional, although there is
code that doesn't honor this (which would be a bug if the fields actually
*were* optional).  When the optionality is honored, there's a performance
risk, especially on platforms with weak or no branch prediction.

Since optional fields makes little sense in a world without hotspot express,
I think these should simply be made non-optional.

Webrev: http://cr.openjdk.java.net/~redestad/8172169/webrev.01
Bug: https://bugs.openjdk.java.net/browse/JDK-8172169

Testing: JPRT pass.

Thanks!

/Claes