Prevent ThreadableLoaderClient methods from being called after failure notification

Source/core/page/EventSource.cpp

Index: Source/core/page/EventSource.cpp
diff --git a/Source/core/page/EventSource.cpp b/Source/core/page/EventSource.cpp
index e05e348067117be7cfd9389a63474d1f28cd5dfc..c2e6a5b93adf15314f71c647ae8a67d8157e3dd1 100644
--- a/Source/core/page/EventSource.cpp
+++ b/Source/core/page/EventSource.cpp
@@ -315,13 +315,10 @@ void EventSource::abortConnectionAttempt()
 {
     ASSERT(m_state == CONNECTING);
 
-    if (m_requestInFlight) {
-        m_loader->cancel();
-    } else {
-        m_state = CLOSED;
-    }
+    m_loader = nullptr;
+    m_state = CLOSED;
+    networkRequestEnded();
 
-    ASSERT(m_state == CLOSED);
     dispatchEvent(Event::create(EventTypeNames::error));
 }