[Fetch API] Fix ScriptState leak in Fetch API unittests.

Source/modules/fetch/DataConsumerHandleTestUtil.cpp

Index: Source/modules/fetch/DataConsumerHandleTestUtil.cpp
diff --git a/Source/modules/fetch/DataConsumerHandleTestUtil.cpp b/Source/modules/fetch/DataConsumerHandleTestUtil.cpp
index ce6b1cb334e3255129904feb7d983fb26ce96c26..946f8683f24fb3a725f3319504546c1f557b25df 100644
--- a/Source/modules/fetch/DataConsumerHandleTestUtil.cpp
+++ b/Source/modules/fetch/DataConsumerHandleTestUtil.cpp
@@ -44,6 +44,9 @@ void DataConsumerHandleTestUtil::Thread::initialize()
 void DataConsumerHandleTestUtil::Thread::shutdown()
 {
     m_executionContext = nullptr;
+    if (m_scriptState) {
+        m_scriptState->disposePerContextData();
+    }
     m_scriptState = nullptr;
     m_thread->shutdown();
     if (m_isolateHolder) {