Bug 1446346 If an AudioContext hasn't been started, do not bother clamping/jittering the CurrentTime r=padenot

This will resolve several intermittments that were occuring because we would
occasionally get unlucky and have a jitter midpoint of 0, making an unstarted
AudioContext report a CurrentTime of 100us (or 1ms - whatever our clamp value
was.)

MozReview-Commit-ID: 45zXLbB93wP

--HG--
extra : rebase_source : 23ea5964dc49543c2b4ca45890c4c08456e75c73

dom/media/webaudio/AudioContext.cpp

@@ -667,6 +667,12 @@ double
 AudioContext::CurrentTime()
 {
   MediaStream* stream = Destination()->Stream();
+
+  if (!mIsStarted &&
+    stream->StreamTimeToSeconds(stream->GetCurrentTime()) == 0) {
+      return 0;
+  }
+
   // The value of a MediaStream's CurrentTime will always advance forward; it will never
   // reset (even if one rewinds a video.) Therefore we can use a single Random Seed
   // initialized at the same time as the object.