Bug 870167 - Create a mini test framework for Web Audio; r=roc

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rename : content/media/webaudio/test/test_audioBufferSourceNodeLoop.html => content/media/webaudio/test/test_audioBufferSourceNodeEnded.html
extra : rebase_source : 787d1d19b6463906ff9db8cbfb5e61d76a2ab667