https://bugs.webkit.org/show_bug.cgi?id=88957

Reviewed by Darin Adler.

More info @ http://infocenter.arm.com/help/topic/
com.arm.doc.genc007826/Barrier_Litmus_Tests_and_Cookbook_A08.pdf

* wtf/Atomics.h:
(WTF::memoryBarrierAfterLock):
(WTF::memoryBarrierBeforeUnlock): Added memory barrier primitives since
ARMv7 has a weakly ordered memory model.

* wtf/Platform.h: Enabled compare-and-swap on Windows so our spinlock
implementation would continue working on Windows.

* wtf/TCSpinLock.h:
(TCMalloc_SpinLock::Lock):
(TCMalloc_SpinLock::Unlock):
(TCMalloc_SpinLock): Use our compare-and-swap helper function to avoid
rewriting it in assembly here.

Added memory barriers since ARMv7 needs them.

Removed PPC support because our helper function doesn't support PPC.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@120356 268f45cc-cd09-0410-ab3c-d52691b4dbfc