[9] RFR (XS): 8059455: LambdaForm.prepare() does unnecessary work for cached LambdaForms

[Vladimir Ivanov]

https://bugs.openjdk.java.net/browse/JDK-8059455
http://cr.openjdk.java.net/~vlivanov/8059455/webrev.00/

LambdaForm.compileToBytecode() does unnecessary work (constructs 
invokerType & check an assertion) before ensuring that LambdaForm hasn't 
been already compiled. It happens very often for cached LambdaForms.

The fix is to do the check first.

Testing: failed VM tests (timeouts)

Best regards,
Vladimir Ivanov