Fix DCHECK when track status changes in non-playing state

media/test/pipeline_integration_test.cc

Index: media/test/pipeline_integration_test.cc
diff --git a/media/test/pipeline_integration_test.cc b/media/test/pipeline_integration_test.cc
index 2a0e72a9bb72857cfd58fd310139a1df15e04fee..9b0ea1c1a9e56c25cfdb9db5f1eedfba2c5cecea 100644
--- a/media/test/pipeline_integration_test.cc
+++ b/media/test/pipeline_integration_test.cc
@@ -1021,6 +1021,24 @@ TEST_F(PipelineIntegrationTest, PlaybackWithVideoTrackDisabledThenEnabled) {
   EXPECT_HASH_EQ("fd59357dfd9c144ab4fb8181b2de32c3", GetVideoHash());
 }
 
+TEST_F(PipelineIntegrationTest, TrackStatusChangesAfterPipelineEnded) {
+  ASSERT_EQ(PIPELINE_OK, Start("bear-320x240.webm", kHashed));
+  Play();
+  ASSERT_TRUE(WaitUntilOnEnded());

[chcunningham, 2016/08/24 22:16:53]

Is the expectation that waiting until ended will cause the renderer to be
removed due to suspend? IIRC it takes a few seconds for suspend to kick in --
you may not be reliably testing the DCHECK case

[servolk, 2016/08/24 22:46:32]

No, we don't need suspend to happen. After pipeline is ended it transitions into
the kStopped state and that is enough to test that the updated DCHECK in the
pipeline_impl.cc is no longer triggered.

[chcunningham, 2016/08/25 20:45:54]

I don't think this transition to stopped is happening. I patched your change and
added logs to pipeline_impl just before your dcheck:

OnEnabledAudioTracksChanged shared_state_.renderer:0x381e5dca8e20 state_:3
OnEnabledAudioTracksChanged shared_state_.renderer:0x381e5dca8e20 state_:3
OnSelectedVideoTrackChanged shared_state_.renderer:0x381e5dca8e20 state_:3
OnSelectedVideoTrackChanged shared_state_.renderer:0x381e5dca8e20 state_:3

So the state is always 3 (playing) and the renderer pointer is always non-null.
So this test passes before and after your changes to the DCHECK.

+  std::vector<MediaTrack::Id> track_ids;
+  // Disable audio track.
+  pipeline_->OnEnabledAudioTracksChanged(track_ids);
+  // Re-enable audio track.
+  track_ids.push_back("2");
+  pipeline_->OnEnabledAudioTracksChanged(track_ids);
+  // Disable video track.
+  track_ids.clear();
+  pipeline_->OnSelectedVideoTrackChanged(track_ids);
+  // Re-enable video track.
+  track_ids.push_back("1");
+  pipeline_->OnSelectedVideoTrackChanged(track_ids);
+}
+
 TEST_F(PipelineIntegrationTest,
        MAYBE_CLOCKLESS(BasicPlaybackOpusOggTrimmingHashed)) {
   ASSERT_EQ(PIPELINE_OK,