--- a/xpcom/build/PoisonIOInterposerBase.cpp
+++ b/xpcom/build/PoisonIOInterposerBase.cpp
@@ -32,29 +32,29 @@ FileDescriptorToHandle(int aFd)
 {
   return aFd;
 }
 #endif /* if not XP_WIN32 */
 
 using namespace mozilla;
 
 namespace {
+
 struct DebugFilesAutoLockTraits
 {
   typedef PRLock* type;
   typedef const PRLock* const_type;
   static const_type empty() { return nullptr; }
   static void release(type aL) { PR_Unlock(aL); }
 };
 
 class DebugFilesAutoLock : public Scoped<DebugFilesAutoLockTraits>
 {
   static PRLock* Lock;
 public:
-  static void Clear();
   static PRLock* getDebugFileIDsLock()
   {
     // On windows this static is not thread safe, but we know that the first
     // call is from
     // * An early registration of a debug FD or
     // * The call to InitWritePoisoning.
     // Since the early debug FDs are logs created early in the main thread
     // and no writes are trapped before InitWritePoisoning, we are safe.
@@ -70,22 +70,16 @@ public:
   DebugFilesAutoLock()
     : Scoped<DebugFilesAutoLockTraits>(getDebugFileIDsLock())
   {
     PR_Lock(get());
   }
 };
 
 PRLock* DebugFilesAutoLock::Lock;
-void
-DebugFilesAutoLock::Clear()
-{
-  MOZ_ASSERT(Lock != nullptr);
-  Lock = nullptr;
-}
 
 // The ChunkedList<T> class implements, at the high level, a non-iterable
 // list of instances of T. Its goal is to be somehow minimalist for the
 // use case of storing the debug files handles here, with the property of
 // not requiring a lock to look up whether it contains a specific value.
 // It is also chunked in blocks of chunk_size bytes so that its
 // initialization doesn't require a memory allocation, while keeping the
 // possibility to increase its size as necessary. Note that chunks are
@@ -203,17 +197,16 @@ typedef ChunkedList<intptr_t> FdList;
 // an ID is a file descriptor. On Windows it is a file HANDLE.
 FdList&
 getDebugFileIDs()
 {
   static FdList DebugFileIDs;
   return DebugFileIDs;
 }
 
-
 } // namespace
 
 namespace mozilla {
 
 // Auxiliary Method to test if a file descriptor is registered to be ignored
 // by the poisoning IO interposer
 bool
 IsDebugFile(intptr_t aFileID)