Reject re-inserting already decoded frames into FrameBuffer2.

webrtc/modules/video_coding/frame_buffer2_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 498 matching lines @@
   EXPECT_EQ(29805, InsertFrame(29805, 0, 1, false, 29804));
   ExtractFrame();
   EXPECT_EQ(29806, InsertFrame(29806, 0, 1, false, 29805));
   ExtractFrame();
   EXPECT_EQ(33819, InsertFrame(33819, 0, 1, false));
   ExtractFrame();
   EXPECT_EQ(41248, InsertFrame(41248, 0, 1, false));
   ExtractFrame();
 }
 
+TEST_F(TestFrameBuffer2, DuplicateFrames) {
+  EXPECT_EQ(22256, InsertFrame(22256, 0, 1, false));
+  ExtractFrame();
+  EXPECT_EQ(22256, InsertFrame(22256, 0, 1, false));
+}
+
 }  // namespace video_coding
 }  // namespace webrtc