[15] RFR 8245823: Shenandoah: inline/optimize ShenandoahEvacOOMScope

[Zhengyu Gu]

> Hm! I actually thought we optimized ShenandoahHeap::heap() enough not to matter [1]. Reverting
> heap() cache would seem to ditch some of these overloads:
> 
>   131   inline ShenandoahEvacOOMScope();
>   132   inline ShenandoahEvacOOMScope(Thread* t);
>   133   inline ShenandoahEvacOOMScope(ShenandoahHeap* heap);
>   134   inline ShenandoahEvacOOMScope(ShenandoahHeap* heap, Thread* t);
>   135   inline ~ShenandoahEvacOOMScope();
> 
> Thread:current() seems fine to pass, where available, and store locally.

Okay, updated: 
http://cr.openjdk.java.net/~zgu/JDK-8245823/webrev.01/index.html

-Zhengyu