MediaStreamTrack: don't wait to record MediaStreamTrack's whose state is not 'live'
MediaStreamTrack: don't wait to record MediaStreamTrack's whose state is not 'live'

A MSTrack on which stop() has been called has state 'ended'.
With this CL MR avoids waiting for those Tracks.

BUG=596178
TEST= See bug #1:

Steps to reproduce:
1- Go to https://cdn.rawgit.com/cricdecyan/mediarecorder/master/manualtest/index.html
 (note: needs either --enable-blink-features=GetUserMedia flag or
 chrome://flags -> Experimental Web Platform features enabled)
2- Click on GetUserMedia
3- Click on StopLocalAudioTracks to disable all audio tracks.
4- Click on CreateRecorder
5- Click on Start

Review URL: https://codereview.chromium.org/1824933005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#382697}

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