RFR: 8144083 [JVMCI] CompilationResult should be finalized by JVMCI compiler and made effectively final

[Doug Simon]

The CompilationResult object is a mutable object built by a JVMCI compiler backend during code generation. Currently, clients of the compiler are required to finalize construction of a CompilationResult once the compilation has completed. Furthermore, the HotSpotCompiledCode constructor takes a partially-constructed CompilationResult and then completes its construction. This non-locality of mutation is not just bad software design but in this case means a single CompilationResult cannot be used to create multiple HotSpotCompiledCode objects. 

We propose to address this by requiring the JVMCI compiler to do all construction of a CompilationResult and then close it to further updating.

https://bugs.openjdk.java.net/browse/JDK-8144083
http://cr.openjdk.java.net/~dnsimon/8144083/

-Doug