RFR(M): 8235988: [c2] Memory leaks during tracing after '8224193: stringStream should not use Resouce Area'.

[Lindenmaier, Goetz]

Hi,

PrintInlining and TraceLoopPredicate allocate stringStreams with new and
relied on the fact that all memory used is on the ResourceArea cleaned
after the compilation.

Since 8224193 the char* of the stringStream is malloced and thus
must be freed. No doing so manifests a memory leak.
This is only relevant if the corresponding tracing is active.

To fix TraceLoopPredicate I added the destructor call.
Fixing PrintInlining is a bit more complicated, as it uses several
stringStreams. A row of them is in a GrowableArray which must
be walked to free all of them.
As the GrowableArray is on an arena no destructor is called for it.

I also changed some as_string() calls to base() calls which reduced
memory need of the traces, and added a comment explaining the
constructor of GrowableArray that calls the copyconstructor for its
elements.

Please review:
http://cr.openjdk.java.net/~goetz/wr19/8235988-c2_tracing_mem_leak/01/

Best regards,
  Goetz.