Add a deinterleaved float interface to AudioProcessing.

This is mainly to support the native audio format in Chrome. Although
this implementation just moves the float->int conversion under the hood,
we will transition AudioProcessing towards supporting this format
throughout.

- Add a test which verifies we get identical output with the float and
int interfaces.
- The float and int wrappers are tasked with conversion to the
AudioBuffer format. A new shared Process/Analyze method does most of
the work.
- Add a new field to the debug.proto to hold deinterleaved data.
- Add helpers to audio_utils.cc, and start using numeric_limits.
- Note that there was no performance difference between numeric_limits
and a literal value when measured on Linux using gcc or clang.

BUG=2894
R=aluebs@webrtc.org, bjornv@webrtc.org, henrikg@webrtc.org, tommi@webrtc.org, turaj@webrtc.org, xians@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9179004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5641 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/audio_processing/audio_buffer.h b/webrtc/modules/audio_processing/audio_buffer.h
index 2638bef..1030fec 100644
--- a/webrtc/modules/audio_processing/audio_buffer.h
+++ b/webrtc/modules/audio_processing/audio_buffer.h
@@ -46,17 +46,28 @@
 
   bool is_muted() const;
 
+  // Use for int16 interleaved data.
   void DeinterleaveFrom(AudioFrame* audioFrame);
   void InterleaveTo(AudioFrame* audioFrame) const;
   // If |data_changed| is false, only the non-audio data members will be copied
   // to |frame|.
   void InterleaveTo(AudioFrame* frame, bool data_changed) const;
+
+  // Use for float deinterleaved data.
+  void CopyFrom(const float* const* data, int samples_per_channel,
+                int num_channels);
+  void CopyTo(int samples_per_channel, int num_channels,
+              float* const* data) const;
+
   void Mix(int num_mixed_channels);
   void CopyAndMix(int num_mixed_channels);
   void CopyAndMixLowPass(int num_mixed_channels);
   void CopyLowPassToReference();
 
  private:
+  // Called from DeinterleaveFrom() and CopyFrom().
+  void InitForNewData(int num_channels);
+
   const int max_num_channels_;
   int num_channels_;
   int num_mixed_channels_;