Reland "NetEq: Deprecate playout modes Fax, Off and Streaming"

This is a reland of 80c4cca4915dbc6094a5bfae749f85f7371eadd1

Original change's description:
> NetEq: Deprecate playout modes Fax, Off and Streaming
> 
> The playout modes other than Normal have not been reachable for a long
> time, other than through tests. It is time to deprecate them.
> 
> The only meaningful use was that Fax mode was sometimes set from
> tests, in order to avoid time-stretching operations (accelerate and
> pre-emptive expand) from messing with the test results. With this CL,
> a new config is added instead, which lets the user specify exactly
> this: don't do time-stretching.
> 
> As a result of Fax and Off modes being removed, the following code
> clean-up was done:
> - Fold DecisionLogicNormal into DecisionLogic.
> - Remove AudioRepetition and AlternativePlc operations, since they can
>   no longer be reached.
> 
> Bug: webrtc:9421
> Change-Id: I651458e9c1931a99f3b07e242817d303bac119df
> Reviewed-on: https://webrtc-review.googlesource.com/84123
> Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
> Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
> Reviewed-by: Minyue Li <minyue@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#23704}

Bug: webrtc:9421
Change-Id: Ice351b635788167f2971b26470f73a5e5fa1a240
Reviewed-on: https://webrtc-review.googlesource.com/86543
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23799}
diff --git a/modules/audio_coding/neteq/neteq_impl.h b/modules/audio_coding/neteq/neteq_impl.h
index 6f69680..6b8764d 100644
--- a/modules/audio_coding/neteq/neteq_impl.h
+++ b/modules/audio_coding/neteq/neteq_impl.h
@@ -168,16 +168,6 @@
 
   int FilteredCurrentDelayMs() const override;
 
-  // Sets the playout mode to |mode|.
-  // Deprecated.
-  // TODO(henrik.lundin) Delete.
-  void SetPlayoutMode(NetEqPlayoutMode mode) override;
-
-  // Returns the current playout mode.
-  // Deprecated.
-  // TODO(henrik.lundin) Delete.
-  NetEqPlayoutMode PlayoutMode() const override;
-
   // Writes the current network statistics to |stats|. The statistics are reset
   // after the call.
   int NetworkStatistics(NetEqNetworkStatistics* stats) override;
@@ -336,12 +326,6 @@
   int DoDtmf(const DtmfEvent& dtmf_event, bool* play_dtmf)
       RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_sect_);
 
-  // Produces packet-loss concealment using alternative methods. If the codec
-  // has an internal PLC, it is called to generate samples. Otherwise, the
-  // method performs zero-stuffing.
-  void DoAlternativePlc(bool increase_timestamp)
-      RTC_EXCLUSIVE_LOCKS_REQUIRED(crit_sect_);
-
   // Overdub DTMF on top of |output|.
   int DtmfOverdub(const DtmfEvent& dtmf_event,
                   size_t num_channels,
@@ -429,7 +413,6 @@
       RTC_GUARDED_BY(crit_sect_);
   uint32_t ssrc_ RTC_GUARDED_BY(crit_sect_);
   bool first_packet_ RTC_GUARDED_BY(crit_sect_);
-  NetEqPlayoutMode playout_mode_ RTC_GUARDED_BY(crit_sect_);
   bool enable_fast_accelerate_ RTC_GUARDED_BY(crit_sect_);
   std::unique_ptr<NackTracker> nack_ RTC_GUARDED_BY(crit_sect_);
   bool nack_enabled_ RTC_GUARDED_BY(crit_sect_);
@@ -441,6 +424,7 @@
   std::vector<uint32_t> last_decoded_timestamps_ RTC_GUARDED_BY(crit_sect_);
   ExpandUmaLogger expand_uma_logger_ RTC_GUARDED_BY(crit_sect_);
   ExpandUmaLogger speech_expand_uma_logger_ RTC_GUARDED_BY(crit_sect_);
+  bool no_time_stretching_ RTC_GUARDED_BY(crit_sect_);  // Only used for test.
 
  private:
   RTC_DISALLOW_COPY_AND_ASSIGN(NetEqImpl);