Replace OS::NumberOfCores() with CPU::NumberOfProcessorsOnline().

Replace OS::NumberOfCores() with CPU::NumberOfProcessorsOnline().

The name NumberOfCores is misleading, as it does not return the
actual number of cores. While NumberOfProcessorsOnline is also
not a great name, it's at least consistent with the operating
system terminology.

R=verwaest@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16392

[Benedikt Meurer, 2013-08-28 10:49:49]

Hey Toon,
Another method moved out of the platform files. PTAL
-- Benedikt

[Toon Verwaest, 2013-08-28 11:44:57]

lgtm

[Benedikt Meurer, 2013-08-28 12:33:08]

Committed patchset #1 manually as r16392.

[tfarina, 2013-08-31 22:10:46]

https://codereview.chromium.org/23655004/diff/1/src/cpu.cc
File src/cpu.cc (right):

https://codereview.chromium.org/23655004/diff/1/src/cpu.cc#newcode456
src/cpu.cc:456: int CPU::NumberOfProcessorsOnline() {
looks like the ninja implementation is stronger.

see:
https://github.com/martine/ninja/blob/master/src/util.cc#L303

[Benedikt Meurer, 2013-09-01 08:32:43]

https://codereview.chromium.org/23655004/diff/1/src/cpu.cc
File src/cpu.cc (right):

https://codereview.chromium.org/23655004/diff/1/src/cpu.cc#newcode456
src/cpu.cc:456: int CPU::NumberOfProcessorsOnline() {
On 2013/08/31 22:10:46, tfarina wrote:
> looks like the ninja implementation is stronger.
> 
> see:
> https://github.com/martine/ninja/blob/master/src/util.cc#L303

No, just unnecessarily complex:
- The BSDs implement sysconf(_SC_NPROCESSORS_ONLN) in terms of sysctl({CTL_HW,
HW_NCPU}), and at least FreeBSD attempts to use ELF aux info if available.
- glibc implements sysconf(_SC_NPROCESSORS_ONLN) in terms of get_nprocs(). And
the #if defined(linux) is broken, because get_nprocs() is a glibc extension and
has nothing to do with Linux.
So basically we have 20 fewer lines, for exactly the same result.