Don't update frame statistics when the frame queue is empty.

This will overflow the -1 iterator in the for loop there.  As a
consequence of this change, we won't update frame statistics when
there's only 1 frame in the queue either.  Which is fine, all
methods which need this information up to date make their own
calls to update the frame statistics.

BUG=498885,498525
TEST=new unittests

Review URL: https://codereview.chromium.org/1178993002

Cr-Commit-Position: refs/heads/master@{#334025}

3 files changed, 36 insertions, 1 deletions

diff --git a/media/filters/video_renderer_algorithm.cc b/media/filters/video_renderer_algorithm.cc
index 233c130..bbb4864 100644
--- a/media/filters/video_renderer_algorithm.cc
+++ b/media/filters/video_renderer_algorithm.cc
@@ -246,10 +246,10 @@ size_t VideoRendererAlgorithm::RemoveExpiredFrames(base::TimeTicks deadline) {
   if (deadline > last_deadline_max_)
     last_deadline_max_ = deadline;
 
-  UpdateFrameStatistics();
   if (frame_queue_.size() < 2)
     return 0;
 
+  UpdateFrameStatistics();
   DCHECK_GT(average_frame_duration_, base::TimeDelta());
 
   // Finds and removes all frames which are too old to be used; I.e., the end of
diff --git a/media/filters/video_renderer_algorithm_unittest.cc b/media/filters/video_renderer_algorithm_unittest.cc
index fcdedd6..9f2a033 100644
--- a/media/filters/video_renderer_algorithm_unittest.cc
+++ b/media/filters/video_renderer_algorithm_unittest.cc
@@ -1038,6 +1038,9 @@ TEST_F(VideoRendererAlgorithmTest, CadenceCalculations) {
 TEST_F(VideoRendererAlgorithmTest, RemoveExpiredFrames) {
   TickGenerator tg(tick_clock_->NowTicks(), 50);
 
+  // Removing expired frames before anything is enqueued should do nothing.
+  ASSERT_EQ(0u, algorithm_.RemoveExpiredFrames(tg.current()));
+
   algorithm_.EnqueueFrame(CreateFrame(tg.interval(0)));
   ASSERT_EQ(0u, algorithm_.RemoveExpiredFrames(tg.current()));
   EXPECT_EQ(1u, algorithm_.EffectiveFramesQueued());
diff --git a/media/renderers/video_renderer_impl_unittest.cc b/media/renderers/video_renderer_impl_unittest.cc
index 75c599e..67cc312 100644
--- a/media/renderers/video_renderer_impl_unittest.cc
+++ b/media/renderers/video_renderer_impl_unittest.cc
@@ -716,6 +716,38 @@ TEST_P(VideoRendererImplTest, RenderingStartedThenStopped) {
   Destroy();
 }
 
+TEST_P(VideoRendererImplTest, StartPlayingFromThenFlushThenEOS) {
+  // This test is only for the new rendering path.
+  if (!GetParam())
+    return;
+
+  Initialize();
+  QueueFrames("0 30 60 90");
+
+  WaitableMessageLoopEvent event;
+  EXPECT_CALL(mock_cb_, FrameReceived(HasTimestamp(0)));
+  EXPECT_CALL(mock_cb_, BufferingStateChange(BUFFERING_HAVE_ENOUGH))
+      .WillOnce(RunClosure(event.GetClosure()));
+  StartPlayingFrom(0);
+  event.RunAndWait();
+
+  // Cycle ticking so that we get a non-null reference time.
+  time_source_.StartTicking();
+  time_source_.StopTicking();
+
+  // Flush and simulate a seek past EOS, where some error prevents the decoder
+  // from returning any frames.
+  EXPECT_CALL(mock_cb_, BufferingStateChange(BUFFERING_HAVE_NOTHING));
+  Flush();
+
+  StartPlayingFrom(200);
+  WaitForPendingRead();
+  SatisfyPendingReadWithEndOfStream();
+  EXPECT_CALL(mock_cb_, BufferingStateChange(BUFFERING_HAVE_ENOUGH));
+  WaitForEnded();
+  Destroy();
+}
+
 INSTANTIATE_TEST_CASE_P(OldVideoRenderer,
                         VideoRendererImplTest,
                         testing::Values(false));