WeakPtrImplBaseSingleThread should cast this to Derived before callin…

…g delete

https://bugs.webkit.org/show_bug.cgi?id=274240

Reviewed by Chris Dumez.

Cast this to Derived* before invoking delete operator on it.

* Source/WTF/wtf/WeakPtrImpl.h:
(WTF::WeakPtrImplBaseSingleThread::deref const):

Canonical link: https://commits.webkit.org/278849@main

Source/WTF/wtf/WeakPtrImpl.h

@@ -116,7 +116,7 @@ class WeakPtrImplBaseSingleThread {
     {
         uint32_t tempRefCount = m_refCount - 1;
         if (!tempRefCount) {
-            delete this;
+            delete const_cast<Derived*>(static_cast<const Derived*>(this));
             return;
         }
         m_refCount = tempRefCount;