Initialize media timeline correctly for positive start times.

media/base/pipeline.cc

Index: media/base/pipeline.cc
diff --git a/media/base/pipeline.cc b/media/base/pipeline.cc
index 086dd9651b16cdc4f7106d9a44e404ab23a8fa3c..ee742bf408b4193a280e07347fbf25ee3cc88713 100644
--- a/media/base/pipeline.cc
+++ b/media/base/pipeline.cc
@@ -343,10 +343,12 @@ void Pipeline::StateTransitionTask(PipelineStatus status) {
       if (!is_initialized_) {
         is_initialized_ = true;
         ReportMetadata();
+        start_timestamp_ = demuxer_->GetStartTime();
       }
 
       base::ResetAndReturn(&seek_cb_).Run(PIPELINE_OK);
 
+      DCHECK(start_timestamp_ >= base::TimeDelta());

[scherkus (not reviewing), 2014/09/16 00:16:51]

is it actually possible to craft such a file? if so, what happens in release
build? is this something we care about?

(IOW, DCHECK -> CHECK?)

[DaleCurtis, 2014/09/16 01:17:46]

I don't think it should be a CHECK, just a DCHECK. It's something that the API
contract says shouldn't be possible. It could only ever happen if Blink let
through a negative seek or GetStartTime() fails its contract.

       renderer_->StartPlayingFrom(start_timestamp_);
 
       if (text_renderer_)
@@ -584,13 +586,16 @@ void Pipeline::SeekTask(TimeDelta time, const PipelineStatusCB& seek_cb) {
 
   DCHECK(seek_cb_.is_null());
 
+  const base::TimeDelta seek_timestamp =
+      std::max(time, demuxer_->GetStartTime());

[scherkus (not reviewing), 2014/09/16 00:07:31]

do we need to update pipeline_unittest.cc? IIRC we have a
StrictMock<MockDemuxer> and it'd be nice to have at least one test that verifies
we're using the right time

[DaleCurtis, 2014/09/16 01:17:46]

Done.

+
   SetState(kSeeking);
   seek_cb_ = seek_cb;
   renderer_ended_ = false;
   text_renderer_ended_ = false;
-  start_timestamp_ = time;
+  start_timestamp_ = seek_timestamp;
 
-  DoSeek(time,
+  DoSeek(seek_timestamp,
          base::Bind(&Pipeline::OnStateTransition, weak_factory_.GetWeakPtr()));
 }