Reject re-inserting already decoded frames into FrameBuffer2.

webrtc/modules/video_coding/frame_buffer2.cc

Index: webrtc/modules/video_coding/frame_buffer2.cc
diff --git a/webrtc/modules/video_coding/frame_buffer2.cc b/webrtc/modules/video_coding/frame_buffer2.cc
index acc1bb83c5a0e448e030d42b98eab5d25315b0a1..727830232c58adee9f8cb1bd57dc76484128a592 100644
--- a/webrtc/modules/video_coding/frame_buffer2.cc
+++ b/webrtc/modules/video_coding/frame_buffer2.cc
@@ -210,7 +210,7 @@ int FrameBuffer::InsertFrame(std::unique_ptr<FrameObject> frame) {
   }
 
   if (last_decoded_frame_it_ != frames_.end() &&
-      key < last_decoded_frame_it_->first) {
+      key <= last_decoded_frame_it_->first) {
     if (AheadOf(frame->timestamp, last_decoded_frame_timestamp_) &&
         frame->num_references == 0) {
       // If this frame has a newer timestamp but an earlier picture id then we