Fix incorrect AudioConverter setup for discrete channel layouts.

media/base/fake_audio_render_callback.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include <cmath>
 
 #include "media/base/fake_audio_render_callback.h"
 
 namespace media {
 
 FakeAudioRenderCallback::FakeAudioRenderCallback(double step)
     : half_fill_(false),
       step_(step),
       last_audio_delay_milliseconds_(-1),
+      last_channel_count_(-1),
       volume_(1) {
   reset();
 }
 
 FakeAudioRenderCallback::~FakeAudioRenderCallback() {}
 
 int FakeAudioRenderCallback::Render(AudioBus* audio_bus,
                                     int audio_delay_milliseconds) {
   last_audio_delay_milliseconds_ = audio_delay_milliseconds;
+  last_channel_count_ = audio_bus->channels();
+
   int number_of_frames = audio_bus->frames();
   if (half_fill_)
     number_of_frames /= 2;
 
   // Fill first channel with a sine wave.
   for (int i = 0; i < number_of_frames; ++i)
     audio_bus->channel(0)[i] = sin(2 * M_PI * (x_ + step_ * i));
   x_ += number_of_frames * step_;
 
   // Copy first channel into the rest of the channels.
   for (int i = 1; i < audio_bus->channels(); ++i)
     memcpy(audio_bus->channel(i), audio_bus->channel(0),
            number_of_frames * sizeof(*audio_bus->channel(i)));
 
   return number_of_frames;
 }
 
 double FakeAudioRenderCallback::ProvideInput(AudioBus* audio_bus,
                                              base::TimeDelta buffer_delay) {
   Render(audio_bus, buffer_delay.InMillisecondsF() + 0.5);
   return volume_;
 }
 
 }  // namespace media