Further test debugging

Now passing:

WebVTTNoBOM
WebVTTWithBOM
WebVTTSpace
WebVTTTab
WebVTTTabText
WebVTTSpaceText
TextBeforeHeader
BlankFile
BlankFileWithBOM
TabAfterBOMBeforeHeader
HeaderNoNewLine
NoPayloadText
MissingCueIdentifier
BOMGarbageNoWebVTT
ExtraNewlinesAfterCue
MultiCueNoNewlineBetweenCues
MultiCueNoPayload
NewlineBeforeWebVTT
NewlineBetweenPayloadText
NewlinesAtTheEnd
BOMGarbageData

Still failing:
BOMTabWebvtt
MissingNewLineBetweenCues