AK: Remove thread safety gunk from userspace WeakPtr

The implicit thread safety stuff is only needed by the kernel version
of WeakPtr, as userspace already makes no guarantees about this.

AK/WeakPtr.h

@@ -153,40 +153,10 @@ template<typename T>
 template<typename U>
 inline WeakPtr<U> Weakable<T>::make_weak_ptr() const
 {
-    if constexpr (IsBaseOf<RefCountedBase, T>) {
-        // Checking m_being_destroyed isn't sufficient when dealing with
-        // a RefCounted type.The reference count will drop to 0 before the
-        // destructor is invoked and revoke_weak_ptrs is called. So, try
-        // to add a ref (which should fail if the ref count is at 0) so
-        // that we prevent the destructor and revoke_weak_ptrs from being
-        // triggered until we're done.
-        if (!static_cast<const T*>(this)->try_ref())
-            return {};
-    } else {
-        // For non-RefCounted types this means a weak reference can be
-        // obtained until the ~Weakable destructor is invoked!
-        if (m_being_destroyed.load(AK::MemoryOrder::memory_order_acquire))
-            return {};
-    }
-    if (!m_link) {
-        // There is a small chance that we create a new WeakLink and throw
-        // it away because another thread beat us to it. But the window is
-        // pretty small and the overhead isn't terrible.
-        m_link.assign_if_null(adopt_ref(*new WeakLink(const_cast<T&>(static_cast<const T&>(*this)))));
-    }
-
-    WeakPtr<U> weak_ptr(m_link);
-
-    if constexpr (IsBaseOf<RefCountedBase, T>) {
-        // Now drop the reference we temporarily added
-        if (static_cast<const T*>(this)->unref()) {
-            // We just dropped the last reference, which should have called
-            // revoke_weak_ptrs, which should have invalidated our weak_ptr
-            VERIFY(!weak_ptr.strong_ref());
-            return {};
-        }
-    }
-    return weak_ptr;
+    if (!m_link)
+        m_link = adopt_ref(*new WeakLink(const_cast<T&>(static_cast<T const&>(*this))));
+
+    return WeakPtr<U>(m_link);
 }
 
 template<typename T>

AK/Weakable.h

@@ -113,7 +113,9 @@ protected:
 
     ~Weakable()
     {
+#ifdef KERNEL
         m_being_destroyed.store(true, AK::MemoryOrder::memory_order_release);
+#endif
         revoke_weak_ptrs();
     }
 
@@ -125,7 +127,9 @@ protected:
 
 private:
     mutable RefPtr<WeakLink> m_link;
+#ifdef KERNEL
     Atomic<bool> m_being_destroyed { false };
+#endif
 };
 
 }