Revert of Switch wtf/SpinLock to std::atomic

third_party/WebKit/Source/wtf/AddressSpaceRandomization.cpp

 // Copyright 2014 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/AddressSpaceRandomization.h"
 
 #include "wtf/PageAllocator.h"
 #include "wtf/SpinLock.h"
 
 #if OS(WIN)
 #include <windows.h>
 #else
 #include <sys/time.h>
 #include <unistd.h>
 #endif
 
 namespace WTF {
 
 namespace {
 
 // This is the same PRNG as used by tcmalloc for mapping address randomness;
 // see http://burtleburtle.net/bob/rand/smallprng.html
 struct ranctx {
-    SpinLock lock;
+    int lock;
     bool initialized;
     uint32_t a;
     uint32_t b;
     uint32_t c;
     uint32_t d;
 };
 
 #define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
 
 uint32_t ranvalInternal(ranctx* x)
 {
     uint32_t e = x->a - rot(x->b, 27);
     x->a = x->b ^ rot(x->c, 17);
     x->b = x->c + x->d;
     x->c = x->d + e;
     x->d = e + x->a;
     return x->d;
 }
 
 #undef rot
 
 uint32_t ranval(ranctx* x)
 {
-    SpinLock::Guard guard(x->lock);
+    spinLockLock(&x->lock);
     if (UNLIKELY(!x->initialized)) {
         x->initialized = true;
         char c;
         uint32_t seed = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(&c));
         uint32_t pid;
         uint32_t usec;
 #if OS(WIN)
         pid = GetCurrentProcessId();
         SYSTEMTIME st;
         GetSystemTime(&st);
         usec = static_cast<uint32_t>(st.wMilliseconds * 1000);
 #else
         pid = static_cast<uint32_t>(getpid());
         struct timeval tv;
         gettimeofday(&tv, 0);
         usec = static_cast<uint32_t>(tv.tv_usec);
 #endif
         seed ^= pid;
         seed ^= usec;
         x->a = 0xf1ea5eed;
         x->b = x->c = x->d = seed;
         for (int i = 0; i < 20; ++i) {
             (void) ranvalInternal(x);
         }
     }
     uint32_t ret = ranvalInternal(x);
+    spinLockUnlock(&x->lock);
     return ret;
 }
 
 static struct ranctx s_ranctx;
 
 }
 
 // Calculates a random preferred mapping address. In calculating an
 // address, we balance good ASLR against not fragmenting the address
 // space too badly.
@@ skipping 39 matching lines @@
     // This is a good range on Windows, Linux and Mac.
     // Allocates in the 0.5-1.5GB region.
     random &= 0x3fffffff;
     random += 0x20000000;
 #endif // CPU(X86_64)
     random &= kPageAllocationGranularityBaseMask;
     return reinterpret_cast<void*>(random);
 }
 
 }