Drop VP8 frames older than the last sync frame in the RtpFrameReferenceFinder.

webrtc/modules/video_coding/rtp_frame_reference_finder_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 579 matching lines @@
   ASSERT_EQ(7UL, frames_from_callback_.size());
   CheckReferencesVp8(pid);
   CheckReferencesVp8(pid + 1, pid);
   CheckReferencesVp8(pid + 2, pid);
   CheckReferencesVp8(pid + 4, pid + 2);
   CheckReferencesVp8(pid + 5, pid + 4);
   CheckReferencesVp8(pid + 6, pid + 4);
   CheckReferencesVp8(pid + 7, pid + 6, pid + 5);
 }
 
+TEST_F(TestRtpFrameReferenceFinder, Vp8Tl1SyncFrameAfterTl1Frame) {
+  InsertVp8(1000, 1000, true, 1, 0, 247, true);
+  InsertVp8(1001, 1001, false, 3, 0, 248, false);
+  InsertVp8(1002, 1002, false, 4, 1, 248, false);  // Will be dropped
+  InsertVp8(1003, 1003, false, 5, 1, 248, true);   // due to this frame.
+
+  ASSERT_EQ(3UL, frames_from_callback_.size());
+  CheckReferencesVp8(1);
+  CheckReferencesVp8(3, 1);
+  CheckReferencesVp8(5, 3);
+}
+
 TEST_F(TestRtpFrameReferenceFinder, Vp9GofInsertOneFrame) {
   uint16_t pid = Rand();
   uint16_t sn = Rand();
   GofInfoVP9 ss;
   ss.SetGofInfoVP9(kTemporalStructureMode1);
 
   InsertVp9Gof(sn, sn, true, pid, 0, 0, 0, false, &ss);
 
   CheckReferencesVp9(pid, 0);
 }
@@ skipping 594 matching lines @@
   CheckReferencesVp9(pid + 5, 1, pid + 4);
   CheckReferencesVp9(pid + 6, 0, pid + 4);
   CheckReferencesVp9(pid + 6, 1, pid + 5);
   CheckReferencesVp9(pid + 7, 1, pid + 6);
   CheckReferencesVp9(pid + 8, 0, pid + 6);
   CheckReferencesVp9(pid + 8, 1, pid + 7);
 }
 
 }  // namespace video_coding
 }  // namespace webrtc