ReadableStream initial implementation

Source/core/streams/UnderlyingSource.h

Index: Source/core/streams/UnderlyingSource.h
diff --git a/Source/core/streams/UnderlyingSource.h b/Source/core/streams/UnderlyingSource.h
new file mode 100644
index 0000000000000000000000000000000000000000..60c3fb38a6b1337970d1a57139fbc498126a57c2
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+++ b/Source/core/streams/UnderlyingSource.h
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+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UnderlyingSource_h
+#define UnderlyingSource_h
+
+#include "platform/heap/Heap.h"
+
+namespace blink {
+
+class ExceptionState;
+
+class UnderlyingSource : public GarbageCollectedFinalized<UnderlyingSource> {
+public:
+    virtual ~UnderlyingSource() { }
+    virtual ScriptPromise startSource(ExceptionState*) = 0;
+    virtual void pullSource(ExceptionState*) = 0;
+    virtual void cancelSource(ExceptionState*) = 0;
+    virtual void trace(Visitor*) { }
+};
+
+} // namespace blink
+
+#endif // UnderlyingSource_h
+