Fix seeking back in the new MSE GC algorithm

media/filters/chunk_demuxer_unittest.cc

Index: media/filters/chunk_demuxer_unittest.cc
diff --git a/media/filters/chunk_demuxer_unittest.cc b/media/filters/chunk_demuxer_unittest.cc
index 99299ac305dd0f346d3862b44188b8740a6cbb26..93cec328d2c92ed1107c4368cd049bfc3598ae40 100644
--- a/media/filters/chunk_demuxer_unittest.cc
+++ b/media/filters/chunk_demuxer_unittest.cc
@@ -3412,6 +3412,19 @@ TEST_F(ChunkDemuxerTest, GCDuringSeek) {
   CheckExpectedRanges(kSourceId, "{ [500,615) [700,815) }");
 }
 
+TEST_F(ChunkDemuxerTest, GCDuringSeekBack) {
+  ASSERT_TRUE(InitDemuxer(HAS_AUDIO));
+  demuxer_->SetMemoryLimits(DemuxerStream::AUDIO, 10 * kBlockSize);
+  // Append some data at position 1000ms
+  AppendSingleStreamCluster(kSourceId, kAudioTrackNum, 1000, 10);
+  CheckExpectedRanges(kSourceId, "{ [1000,1230) }");
+
+  // GC should be able to evict frames in the currently buffered range, since
+  // those frames are later than the seek target position 0.
+  base::TimeDelta seek_time = base::TimeDelta::FromMilliseconds(0);
+  EXPECT_TRUE(demuxer_->EvictCodedFrames(kSourceId, seek_time, 5 * kBlockSize));

[wolenetz, 2015/09/16 19:25:27]

nit: We could do a further check of expectation here that the resulting buffered
ranges after GC of 5 blocks is now { [ 1115,1230) } IIUC.

Also, it would be good to have a variety of related GC-while-unsatisfied-seek
tests:
1) this one
2) three buffered ranges, seek time is between first and second, last append is
at end of third range; ensure that GC can collect from front into the middle of
the third range (or maybe a 2b. case that also tests that *all* could be
collected).
3) a couple buffered ranges with seek time between them and last appended buffer
was at end of the *first* range.

I'm probably missing one or two major test details here, but you get the point:
I don't think we previously had nearly enough unsatisfied-seek-and-GC test
coverage. This one test is great; I would like more.

+}
+
 TEST_F(ChunkDemuxerTest, GCKeepPlayhead) {
   ASSERT_TRUE(InitDemuxer(HAS_AUDIO));