https://bugs.webkit.org/show_bug.cgi?id=123107

Reviewed by Geoffrey Garen.

* runtime/JSLock.cpp:
(JSC::JSLock::unlock):
(JSC::JSLock::dropAllLocks): Modified to take a SpinLock, used only on iOS.
(JSC::JSLock::dropAllLocksUnconditionally): Modified to take a SpinLock, used only on iOS. Also
use pre-increment instead of post-increment when we're not using the return value of the instruction.
(JSC::JSLock::grabAllLocks): Modified to take a SpinLock, used only on iOS. Also change
places where we were using post-increment/post-decrement to use pre-increment/pre-decrement,
since we don't use the return value of such instructions.
(JSC::JSLock::DropAllLocks::DropAllLocks): Modified to support releasing all locks unconditionally.
Take a spin lock before releasing all locks on iOS. Also, use nullptr instead of 0.
(JSC::JSLock::DropAllLocks::~DropAllLocks): Take a spin lock before acquiring all locks on iOS.
* runtime/JSLock.h: Remove extraneous argument name "exec" from DropAllLocks as the data type of
the argument is sufficiently descriptive of its purpose.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@157809 268f45cc-cd09-0410-ab3c-d52691b4dbfc