Problem Description:  SourceBuffer AppendStream has a MaxSize attribute that has type unsigned long long with no restriction.  Some behaviors for AppendStream would be unsuitable.  For instance, if MaxSize was set to infinity, unsigned long long would return a value of 0.  

 
Proposed Change: Modify the WebIDL for SourceBuffer to add EnforceRange to MaxSize:

interface SourceBuffer : EventTarget {
    readonly    attribute boolean             updating;
    readonly    attribute TimeRanges          buffered;
                attribute double              timestampOffset;
    readonly    attribute AudioTrackList      audioTracks;
    readonly    attribute VideoTrackList      videoTracks;
    readonly    attribute TextTrackList       textTracks;
                attribute double              appendWindowStart;
                attribute unrestricted double appendWindowEnd;
    void appendBuffer (ArrayBuffer data);
    void appendBuffer (ArrayBufferView data);
    void appendStream (Stream stream, optional [EnforceRange] unsigned long long maxSize);
    void abort (optional AbortMode mode);
    void remove (double start, double end);