Preliminary work for unprefixed MSE SourceBuffer.mode manipulation

Source/modules/mediasource/SourceBuffer.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 [
     NoInterfaceObject,
     ActiveDOMObject,
     RuntimeEnabled=MediaSource
 ] interface SourceBuffer : EventTarget {
 
+    // Gets or sets the AppendMode.
+    // FIXME: Remove MediaSourceExperimental once mode attribute is implemented and stabilized. See http://crbug.com/249422.
+    [RaisesException=Setter, RuntimeEnabled=MediaSourceExperimental] attribute DOMString mode;
+
     readonly attribute boolean updating;
 
     // Returns the time ranges buffered.
     [RaisesException=Getter] readonly attribute TimeRanges buffered;
 
     // Applies an offset to media segment timestamps.
     [RaisesException=Setter] attribute double timestampOffset;
 
     // Presentation timestamp for the start of append window.
     [RaisesException=Setter] attribute double appendWindowStart;
 
     // Presentation timestamp for the end of append window.
     [RaisesException=Setter] attribute double appendWindowEnd;
 
     // Append segment data.
     [RaisesException] void appendBuffer(ArrayBuffer data);
     [RaisesException] void appendBuffer(ArrayBufferView data);
 
     [RaisesException, RuntimeEnabled=Stream] void appendStream(Stream stream, optional unsigned long long maxSize);
 
     // Abort the current segment append sequence.
     [RaisesException] void abort();
     [RaisesException] void remove(double start, double end);
 };