[Streams] UnderlyingSourceBase should be kept alive only when locked

third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h

Index: third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h
diff --git a/third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h b/third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h
index bba33affad602ddb9626f0348eab651b2d00fb97..642ef896a1cae22efdc226b5f7f1a39104d00ba7 100644
--- a/third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h
+++ b/third_party/WebKit/Source/core/streams/UnderlyingSourceBase.h
@@ -35,6 +35,9 @@ public:
     ScriptPromise cancelWrapper(ScriptState*, ScriptValue reason);
     virtual ScriptPromise cancel(ScriptState*, ScriptValue reason);
 
+    void notifyLockAcquired();
+    void notifyLockReleased();
+
     // ActiveScriptWrappable
     bool hasPendingActivity() const final;
 
@@ -53,6 +56,7 @@ protected:
 
 private:
     Member<ReadableStreamController> m_controller;
+    bool m_isStreamLocked = false;
 };
 
 } // namespace blink