Delete a chain of methods in ViE, VoE and ACM

The end goal is to remove AcmReceiver::SetInitialDelay. This change is
in preparation for that goal. It turns out that
AcmReceiver::SetInitialDelay was only invoked through the following
call chain, where each method in the chain is never referenced from
anywhere else (except from tests in some cases):

ViEChannel::SetReceiverBufferingMode
-> ViESyncModule::SetTargetBufferingDelay
-> VoEVideoSync::SetInitialPlayoutDelay
-> Channel::SetInitialPlayoutDelay
-> AudioCodingModule::SetInitialPlayoutDelay
-> AcmReceiver::SetInitialDelay

The start of the chain, ViEChannel::SetReceiverBufferingMode was never
referenced.

This change deletes all the methods above except
AcmReceiver::SetInitialDelay itself, which will be handled in a
follow-up change.

BUG=webrtc:3520

Review URL: https://codereview.webrtc.org/1421013006

Cr-Commit-Position: refs/heads/master@{#10471}

webrtc/modules/audio_coding/main/include/audio_coding_module.h

@@ -704,23 +704,6 @@ class AudioCodingModule {
   virtual int32_t GetNetworkStatistics(
       NetworkStatistics* network_statistics) = 0;
 
-  //
-  // Set an initial delay for playout.
-  // An initial delay yields ACM playout silence until equivalent of |delay_ms|
-  // audio payload is accumulated in NetEq jitter. Thereafter, ACM pulls audio
-  // from NetEq in its regular fashion, and the given delay is maintained
-  // through out the call, unless channel conditions yield to a higher jitter
-  // buffer delay.
-  //
-  // Input:
-  //   -delay_ms           : delay in milliseconds.
-  //
-  // Return values:
-  //   -1 if failed to set the delay.
-  //    0 if delay is set successfully.
-  //
-  virtual int SetInitialPlayoutDelay(int delay_ms) = 0;
-
   //
   // Enable NACK and set the maximum size of the NACK list. If NACK is already
   // enable then the maximum NACK list size is modified accordingly.