Check current buffer time span instead of number of samples in postpone decoding after expand.

Bug: webrtc:10392
Change-Id: I2ad4d8c7a3f87cab32e2ea097b2e05aa179e0bc0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/126761
Reviewed-by: Minyue Li <minyue@webrtc.org>
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Commit-Queue: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27080}

modules/audio_coding/neteq/packet_buffer.h

@@ -121,6 +121,10 @@ class PacketBuffer {
   // duplicate and redundant packets.
   virtual size_t NumSamplesInBuffer(size_t last_decoded_length) const;
 
+  // Returns the total duration in samples that the packets in the buffer spans
+  // across.
+  virtual size_t GetSpanSamples(size_t last_decoded_length) const;
+
   // Returns true if the packet buffer contains any DTX or CNG packets.
   virtual bool ContainsDtxOrCngPacket(
       const DecoderDatabase* decoder_database) const;