Use the AudioProcessing float interface in MediaStreamAudioProcessor.

media/base/audio_bus.h

 // 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.
 
 #ifndef MEDIA_BASE_AUDIO_BUS_H_
 #define MEDIA_BASE_AUDIO_BUS_H_
 
 #include <vector>
 
 #include "base/memory/aligned_memory.h"
@@ skipping 74 matching lines @@
                            int dest_start_frame,
                            AudioBus* dest) const;
 
   // Returns a raw pointer to the requested channel.  Pointer is guaranteed to
   // have a 16-byte alignment.  Warning: Do not rely on having sane (i.e. not
   // inf, nan, or between [-1.0, 1.0]) values in the channel data.
   float* channel(int channel) { return channel_data_[channel]; }
   const float* channel(int channel) const { return channel_data_[channel]; }
   void SetChannelData(int channel, float* data);
 
+  // Returns an array of pointers to each channel.
+  float** channel_data() { return &channel_data_[0]; }

[tommi (sloooow) - chröme, 2014/08/06 13:45:56]

I would like to get Dale to look at this (and perhaps some of the other changes
if he can).

I'm currently sheriffing so I have time occasionally but not continuously :) 
I'll take another round probably later today.

+  const float* const* channel_data() const { return &channel_data_[0]; }
+
   int channels() const { return static_cast<int>(channel_data_.size()); }
   int frames() const { return frames_; }
   void set_frames(int frames);
 
   // Helper method for zeroing out all channels of audio data.
   void Zero();
   void ZeroFrames(int frames);
   void ZeroFramesPartial(int start_frame, int frames);
 
   // Scale internal channel values by |volume| >= 0.  If an invalid value
@@ skipping 43 matching lines @@
 
   AudioBusRefCounted(int channels, int frames);
   virtual ~AudioBusRefCounted();
 
   DISALLOW_COPY_AND_ASSIGN(AudioBusRefCounted);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_BUS_H_