RFR(XS) 8037959: BitMap::resize frees old map before copying memory if !in_resource_area

[Mikael Gerdin]

Hi all,

While reading through the code for BitMap I stumbled across a bug in the 
resize functionality for bitmaps not allocated in the resource area.

The problem is that if a previous backing for the bitmap exists we free the 
backing memory before attempting to copy its contents to the new backing 
memory.

I've followed the code paths leading to resize so I'm pretty sure this bug is 
currently benign since we never actually encounter this case but it seems like 
a good idea to fix this nevertheless.

Bug: https://bugs.openjdk.java.net/browse/JDK-8037959
Webrev: http://cr.openjdk.java.net/~mgerdin/8037959/webrev.0

/Mikael