Revert of Switch wtf/SpinLock to std::atomic

third_party/WebKit/Source/web/tests/SpinLockTest.cpp

Index: third_party/WebKit/Source/web/tests/SpinLockTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/SpinLockTest.cpp b/third_party/WebKit/Source/web/tests/SpinLockTest.cpp
index 7806b5bb710660837a4542b76f17e509474a9d6f..18abef96e2ecfe6f7b0adb4d3fa976f61400979f 100644
--- a/third_party/WebKit/Source/web/tests/SpinLockTest.cpp
+++ b/third_party/WebKit/Source/web/tests/SpinLockTest.cpp
@@ -44,7 +44,7 @@
 
 static const size_t bufferSize = 16;
 
-static SpinLock lock;
+static int lock = 0;
 
 static void fillBuffer(volatile char* buffer, char fillPattern)
 {
@@ -69,8 +69,9 @@
 static void threadMain(volatile char* buffer)
 {
     for (int i = 0; i < 500000; ++i) {
-        SpinLock::Guard guard(lock);
+        spinLockLock(&lock);
         changeAndCheckBuffer(buffer);
+        spinLockUnlock(&lock);
     }
 }