Introduce ExclusiveStreamReader.

Source/core/streams/ExclusiveStreamReader.idl

Index: Source/core/streams/ExclusiveStreamReader.idl
diff --git a/Source/core/streams/ReadableStream.idl b/Source/core/streams/ExclusiveStreamReader.idl
similarity index 63%
copy from Source/core/streams/ReadableStream.idl
copy to Source/core/streams/ExclusiveStreamReader.idl
index 4e299434d654deab776e747603e310a1db4d00a1..1dc03d0227be5a925c17b766dd269ab6d0ba287c 100644
--- a/Source/core/streams/ReadableStream.idl
+++ b/Source/core/streams/ExclusiveStreamReader.idl
@@ -1,25 +1,22 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
+// 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.
 
-enum ReadableStreamState {
-    "readable",
-    "waiting",
-    "closed",
-    "errored"
-};
-
 [
     RuntimeEnabled=ExperimentalStream,
     GarbageCollected,
-    Exposed=(Window,Worker),
     ActiveDOMObject,
-] interface ReadableStream {
-    [CallWith=ScriptState, RaisesException] any read();
+    Exposed=(Window,Worker),
+] interface ExclusiveStreamReader {
+    // FIXME: Add constructor.
+
+    [CallWith=ScriptState] readonly attribute Promise closed;
+    readonly attribute boolean isActive;
     [CallWith=ScriptState] readonly attribute Promise ready;
-    [ImplementedAs=stateString] readonly attribute ReadableStreamState state;
+    // See ReadableStream.state.
+    readonly attribute DOMString state;
 
     [CallWith=ScriptState] Promise cancel(any reason);
-
-    [CallWith=ScriptState] readonly attribute Promise closed;
+    [CallWith=ScriptState, RaisesException] any read();
+    void releaseLock();
 };