Bug 1002290 - Set MediaSource duration when read by MediaSourceReader - r=kinetik

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extra : rebase_source : 07ac1618cf17fd09b72b4fcf7d1fd2973f989999
Bug 1002294 - Fix ContainsTime in SourceBuffer to allow for gaps in time ranges - r=kinetik

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extra : rebase_source : 6f872c3cd3757f57832cd0797338a1f93b4fa977