GDBJIT: Add gdbjit_zone for --gdbjit_full

GDBJIT: Add gdbjit_zone for --gdbjit_full

[haitao.feng, 2013-03-22 07:29:51]

When --gdbjit_full is used, the CompilationInfo might be null for stubs, ICs,
trampolines and then V8 crashes in the gdb.

I am not sure whether we could use runtime_zone() here, so I introduced
gdbjit_zone in the isolate.h for gdbjit information allocation.

[haitao.feng, 2013-04-07 03:10:31]

Ping.

This patch is needed to solve
https://code.google.com/p/v8/issues/detail?id=2608.

To enable gdbjit for X64, currently we need:
1) Build V8 with snapshot=off gdbjit=on
2) Run V8 with --gdbjit --gdbjit_full

Though we need more investigation on "Dwarf Error: Could not find abbrev number
[in module <in-memory>]".

[Michael Starzinger, 2013-04-09 15:38:02]

The CodeAdd event has to fire after the Code object has been allocated on the
heap and instructions have been copied over, so we need to be back on the main
thread when this event fires. Hence I think it is save to use runtime_zone here.
Can we switch to Isolate::runtime_zone() and drop the changes to the isolate?

[Michael Starzinger, 2013-04-09 15:51:19]

I took the liberty to upload an adapted version of your CL. I wanted to avoid
introducing another usage of Isolate::Current() as we want to phase out TLS
lookup. If you are fine with this adapted version I'll land that instead (with
the proper attribution of course).

See https://codereview.chromium.org/13813014/

[Michael Starzinger, 2013-04-10 08:12:28]

Closed manually because an adapted version landed in r14198.