Make getting the getting number of CPU cores more portable

Special-case only android and windows platforms and for the default case use sysconf() call to get the number of cores.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=157734

[lgombos, 2013-09-12 02:45:51]

Inspired by a comment made by Evan
https://codereview.chromium.org/23536039/#msg17 . 

Similar solution is used now by ninja -
https://github.com/bmeurer/ninja/commit/4a72182c6c65d44f894da68a72fb797b34c8d9ec

[Evan Martin, 2013-09-12 19:01:30]

+nico

[Nico, 2013-09-12 19:34:54]

lgtm

https://codereview.chromium.org/23609031/diff/3001/Source/wtf/NumberOfCores.cpp
File Source/wtf/NumberOfCores.cpp (right):

https://codereview.chromium.org/23609031/diff/3001/Source/wtf/NumberOfCores.c...
Source/wtf/NumberOfCores.cpp:47: // FIXME: Can we do better on Android - perhaps
calling sysconf() ?
luckily we have 20 different implementations of everything in our codebase, so
it's easy to compare notes.

webrtc also does the sysconf call for android:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...

v8 always calls sysconf on non-windows, but not sure if that's intentional on
android:
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/cpu.cc&ct=r...

same for nacl:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/test/nacl/n...

vp8 does a poor job on non-win:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libvpx...
(but supports os2 :-D)

So I guess I'd remove the OS(ANDROID).

[commit-bot: I haz the power, 2013-09-13 01:58:19]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/l.gombos@samsung.com/23609031/10001

[commit-bot: I haz the power, 2013-09-13 03:05:46]

Change committed as 157734