Add noBarrierStore to WTF and use it for spinlocks

third_party/WebKit/Source/wtf/SpinLock.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "wtf/SpinLock.h"
 
 #include "wtf/Atomics.h"
 #include "wtf/CPU.h"
 #include "wtf/Compiler.h"
@@ skipping 44 matching lines @@
 {
     // The value of kYieldProcessorTries is cargo culted from TCMalloc, Windows
     // critical section defaults, and various other recommendations.
     // TODO(jschuh): Further tuning may be warranted.
     static const int kYieldProcessorTries = 1000;
     do {
         do {
             for (int count = 0; count < kYieldProcessorTries; ++count) {
                 // Let the Processor know we're spinning.
                 YIELD_PROCESSOR;
-                if (!*lock && LIKELY(!atomicTestAndSetToOne(lock)))
+                if (!noBarrierLoad(lock) && LIKELY(!atomicTestAndSetToOne(lock)))
                     return;
             }
 
             // Give the OS a chance to schedule something on this core.
             YIELD_THREAD;
-        } while (*lock);
+        } while (noBarrierLoad(lock));
     } while (UNLIKELY(atomicTestAndSetToOne(lock)));
 }
 
 } // namespace WTF