Update selected range after truncation

   
Update |SourceBufferStream::selected_range_| after |TruncateAt| is called in case the range pointed to by it gets deleted.

There are situations where next_buffer_index_ remains at -1 
where|ChunkDemuxer::AppendData| is invoked. This eventually
causes crash. This changes prevents such cases.

The crash is occasionally observed when YouTube MSE/EME
conformance test http://yt-dash-mse-test.commondatastorage.googleapis.com/unit-tests/tot.html
(41.MediaSourceDuration) is done on Android TV device.

BUG=313102

Review URL: https://codereview.chromium.org/51983002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233468 0039d316-1c4b-4281-b951-d872f2087c98

media/filters/source_buffer_stream.cc

@@ -1054,6 +1054,8 @@ void SourceBufferStream::OnSetDuration(base::TimeDelta duration) {
   // Need to partially truncate this range.
   if ((*itr)->GetStartTimestamp() < duration) {
     (*itr)->TruncateAt(duration, NULL, false);
+    if ((*itr == selected_range_) && !selected_range_->HasNextBufferPosition())
+      SetSelectedRange(NULL);
     ++itr;
   }
 

media/filters/source_buffer_stream_unittest.cc

@@ -2864,6 +2864,31 @@ TEST_F(SourceBufferStreamTest, SetExplicitDuration_DeletePartialSelectedRange) {
   CheckExpectedRanges("{ [0,4) [10,10) }");
 }
 
+// Test the case where duration is set while the stream parser buffers
+// already start passing the data to decoding pipeline. Selected range,
+// when invalidated by getting truncated, should be updated to NULL
+// accordingly so that successive append operations keep working.
+TEST_F(SourceBufferStreamTest, SetExplicitDuration_UpdateSelectedRange) {
+  // Seek to start of stream.
+  SeekToTimestamp(base::TimeDelta::FromMilliseconds(0));
+
+  NewSegmentAppend("0K 30 60 90");
+
+  // Read out the first few buffers.
+  CheckExpectedBuffers("0K 30");
+
+  // Set duration to be right before buffer 1.
+  stream_->OnSetDuration(base::TimeDelta::FromMilliseconds(60));
+
+  // Verify that there is no next buffer.
+  CheckNoNextBuffer();
+
+  // We should be able to append new buffers at this point.
+  NewSegmentAppend("120K 150");
+
+  CheckExpectedRangesByTimestamp("{ [0,60) [120,180) }");
+}
+
 // Test the case were the current playback position is at the end of the
 // buffered data and several overlaps occur that causes the selected
 // range to get split and then merged back into a single range.