Introduce ExclusiveStreamReader.

Source/core/streams/ExclusiveStreamReader.h

+// Copyright 2015 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 ExclusiveStreamReader_h
+#define ExclusiveStreamReader_h
+
+#include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptPromiseProperty.h"
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "bindings/core/v8/ToV8.h"
+#include "core/dom/ActiveDOMObject.h"
+#include "core/streams/ReadableStream.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class DOMException;
+class ExceptionState;
+class ScriptState;
+
+// ExclusiveStreamReader corresponds to the same-name class in the Streams spec
+// https://streams.spec.whatwg.org/. This class trusts ReadableStream, contrary
+// to the class in the Streams spec, because we only support
+// blink::Readable[Byte]Stream as this reader's customer.
+class ExclusiveStreamReader final : public GarbageCollectedFinalized<ExclusiveStreamReader>, public ScriptWrappable, public ActiveDOMObject {
+    DEFINE_WRAPPERTYPEINFO();
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(ExclusiveStreamReader);
+public:
+    // The stream must not be locked to any ExclusiveStreamReader when called.
+    ExclusiveStreamReader(ReadableStream*);
+
+    ScriptPromise closed(ScriptState*);
+    bool isActive() const;
+    ScriptPromise ready(ScriptState*);
+    String state() const;
+    ScriptPromise cancel(ScriptState*, ScriptValue reason);
+    ScriptValue read(ScriptState*, ExceptionState&);
+    void releaseLock();
+    ScriptPromise released(ScriptState*);
+
+    bool hasPendingActivity() const override;
+    void stop() override;
+
+    void trace(Visitor*);
+
+private:
+    using ReleasedPromise = ScriptPromiseProperty<Member<ExclusiveStreamReader>, ToV8UndefinedGenerator, ToV8UndefinedGenerator>;
+    using ClosedPromise = ScriptPromiseProperty<Member<ExclusiveStreamReader>, ToV8UndefinedGenerator, RefPtrWillBeMember<DOMException>>;
+    using ReadyPromise = ScriptPromiseProperty<Member<ExclusiveStreamReader>, ToV8UndefinedGenerator, ToV8UndefinedGenerator>;
+
+    const Member<ReadableStream> m_stream;
+    const Member<ReleasedPromise> m_released;
+    ReadableStream::State m_stateAfterRelease;
+    Member<ClosedPromise> m_closedAfterRelease;
+    Member<ReadyPromise> m_readyAfterRelease;
+};
+
+} // namespace blink
+
+#endif // ExclusiveStreamReader_h