AudioBus: Add a ToInterleavedFloat() method to AudioBus

media/cast/sender/audio_encoder.cc

Index: media/cast/sender/audio_encoder.cc
diff --git a/media/cast/sender/audio_encoder.cc b/media/cast/sender/audio_encoder.cc
index bacb793fddbb6b9fd1cfc23de5fca3fcc36fcb66..a67664925f308db80cdc96a651b88b870c78ef40 100644
--- a/media/cast/sender/audio_encoder.cc
+++ b/media/cast/sender/audio_encoder.cc
@@ -283,14 +283,11 @@ class AudioEncoder::OpusImpl : public AudioEncoder::ImplBase {
                                  int source_offset,
                                  int buffer_fill_offset,
                                  int num_samples) final {
+    DCHECK_EQ(audio_bus->channels(), num_channels_);

[mcasas, 2016/04/11 23:47:08]

nit: Expected value goes first, and I 
think in this case that's |num_channels_|.

     // Opus requires channel-interleaved samples in a single array.
-    for (int ch = 0; ch < audio_bus->channels(); ++ch) {
-      const float* src = audio_bus->channel(ch) + source_offset;
-      const float* const src_end = src + num_samples;
-      float* dest = buffer_.get() + buffer_fill_offset * num_channels_ + ch;
-      for (; src < src_end; ++src, dest += num_channels_)
-        *dest = *src;
-    }
+    audio_bus->ToInterleavedFloat(source_offset,
+                                  buffer_fill_offset * num_channels_,
+                                  num_samples, buffer_.get());
   }
 
   bool EncodeFromFilledBuffer(std::string* out) final {