Request a new key frame if packet buffer is cleared

Bug: webrtc:10843
Change-Id: I1eab0891f3e68b7d504dc637790604a25c243856
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/147721
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28735}
diff --git a/modules/video_coding/packet_buffer.h b/modules/video_coding/packet_buffer.h
index 20e0bff..b5264bc 100644
--- a/modules/video_coding/packet_buffer.h
+++ b/modules/video_coding/packet_buffer.h
@@ -49,9 +49,10 @@
 
   virtual ~PacketBuffer();
 
-  // Returns true if |packet| is inserted into the packet buffer, false
-  // otherwise. The PacketBuffer will always take ownership of the
-  // |packet.dataPtr| when this function is called. Made virtual for testing.
+  // Returns true unless the packet buffer is cleared, which means that a key
+  // frame request should be sent. The PacketBuffer will always take ownership
+  // of the |packet.dataPtr| when this function is called. Made virtual for
+  // testing.
   virtual bool InsertPacket(VCMPacket* packet);
   void ClearTo(uint16_t seq_num);
   void Clear();