Fix call of finalized virtual function.

Fix call of finalized virtual function.

In the RegExpUnparser::VisitText(RegExpText* that, void* data) function always RegExpUnparser::VisitAtom function called via that->elements()->at(i).data.u_atom->Accept(this, data); even if the type of the object is RegExpCharacterClass.

The problem comes up using g++ 4.7(.2, .3) sice r16232. Tested on MIPS and x64:
Program received signal SIGSEGV, Segmentation fault.
0x0000000000588928 in v8::internal::RegExpUnparser::VisitAtom(v8::internal::RegExpAtom*, void*) ()

BUG=
TEST=cctest/test-regexp/ParserRegression

[Paul Lind, 2013-08-22 23:24:08]

Thanks Balázs. I separately verified that this segfault occurs on ia32, x64 (and
arm, mips sims) with gcc-4.7.3 on Ubuntu 12.04, as well as on mips hardware. And
that this CL fixes the issue.

But I can't approve this change, can one of the v8 team folks PTAL?

[Benedikt Meurer, 2013-08-23 08:59:29]

Please test the following:

1.) Build with C++11 enabled (i.e. CXXFLAGS=-std=c++11).
2.) Try to remove the V8_FINAL declaration from RegExpAtom.

[Benedikt Meurer, 2013-08-23 09:27:22]

On 2013/08/23 08:59:29, Benedikt Meurer wrote:
> Please test the following:
> 
> 1.) Build with C++11 enabled (i.e. CXXFLAGS=-std=c++11).
> 2.) Try to remove the V8_FINAL declaration from RegExpAtom.

Forget about it. You spotted a bug in V8 here. I'll prepare a fix. :-)

[Benedikt Meurer, 2013-08-23 10:29:00]

On 2013/08/23 09:27:22, Benedikt Meurer wrote:
> On 2013/08/23 08:59:29, Benedikt Meurer wrote:
> > Please test the following:
> > 
> > 1.) Build with C++11 enabled (i.e. CXXFLAGS=-std=c++11).
> > 2.) Try to remove the V8_FINAL declaration from RegExpAtom.
> 
> Forget about it. You spotted a bug in V8 here. I'll prepare a fix. :-)

See https://codereview.chromium.org/22815033/