RefCounted::derefBase() should do the decrement from 1 to 0

Source/wtf/RefCounted.h

Index: Source/wtf/RefCounted.h
diff --git a/Source/wtf/RefCounted.h b/Source/wtf/RefCounted.h
index cdbf81f8ed81b82eff0412d30a600329593c646b..662ae55cb4e9cd398bf42f6c4ac971acd87ed7ab 100644
--- a/Source/wtf/RefCounted.h
+++ b/Source/wtf/RefCounted.h
@@ -118,14 +118,14 @@ protected:
 #endif
 
         ASSERT(m_refCount > 0);
-        if (m_refCount == 1) {
+        --m_refCount;
+        if (!m_refCount) {
 #if SECURITY_ASSERT_ENABLED
             m_deletionHasBegun = true;
 #endif
             return true;
         }
 
-        --m_refCount;
 #if CHECK_REF_COUNTED_LIFECYCLE
         // Stop thread verification when the ref goes to 1 because it
         // is safe to be passed to another thread at this point.