Fix seeking when the start time is non-zero.

media/base/pipeline.cc

Index: media/base/pipeline.cc
diff --git a/media/base/pipeline.cc b/media/base/pipeline.cc
index 46be2b86e6809c592bc554fefdf8ee456b76b14d..8fbc094c1ac0b56f32af4c513009fad9dbbbdaf1 100644
--- a/media/base/pipeline.cc
+++ b/media/base/pipeline.cc
@@ -743,17 +743,21 @@ void Pipeline::SeekTask(TimeDelta time, const PipelineStatusCB& seek_cb) {
   DCHECK(seek_cb_.is_null());
 
   SetState(kSeeking);
-  base::TimeDelta seek_timestamp = std::max(time, demuxer_->GetStartTime());
   seek_cb_ = seek_cb;
   audio_ended_ = false;
   video_ended_ = false;
   text_ended_ = false;
 
+  // Adjust the seek timestamp by the start time (which may be negative).  Don't
+  // use this value with SetTime() since it maps to a [0, duration] based
+  // timeline instead of a [start_time, duration + start_time] one internally.
+  const base::TimeDelta seek_timestamp = time + demuxer_->GetStartTime();
+
   // Kick off seeking!
   {
     base::AutoLock auto_lock(lock_);
     PauseClockAndStopRendering_Locked();
-    clock_->SetTime(seek_timestamp, seek_timestamp);
+    clock_->SetTime(time, time);

[acolwell GONE FROM CHROMIUM, 2014/06/09 23:14:46]

This makes me really nervous and I'm pretty sure it is wrong. I suspect this
will break A/V sync if the start time != 0 unless there is something that is
subtracting off the start time in the demuxer. You should definitely do tests
with muxed A/V content that starts at something significantly greater than 0
before landing this just to make sure you aren't breaking things.

   }
   DoSeek(seek_timestamp, base::Bind(
       &Pipeline::OnStateTransition, base::Unretained(this)));