Add SSE optimizations to AudioRendererMixer.

media/base/audio_renderer_mixer.h

Index: media/base/audio_renderer_mixer.h
diff --git a/media/base/audio_renderer_mixer.h b/media/base/audio_renderer_mixer.h
index 76e68bcbf209629546fc4b99e27f2ca5fd2d405e..d293799266440e9885e37e0ef927ddde14c77bf8 100644
--- a/media/base/audio_renderer_mixer.h
+++ b/media/base/audio_renderer_mixer.h
@@ -8,6 +8,7 @@
 #include <set>
 #include <vector>
 
+#include "base/gtest_prod_util.h"
 #include "base/synchronization/lock.h"
 #include "media/base/audio_renderer_mixer_input.h"
 #include "media/base/audio_renderer_sink.h"
@@ -33,6 +34,9 @@ class MEDIA_EXPORT AudioRendererMixer
   void RemoveMixerInput(const scoped_refptr<AudioRendererMixerInput>& input);
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(AudioRendererMixerTest, VectorFMAC);
+  FRIEND_TEST_ALL_PREFIXES(AudioRendererMixerTest, VectorFMACBenchmark);
+
   // AudioRendererSink::RenderCallback implementation.
   virtual int Render(const std::vector<float*>& audio_data,
                      int number_of_frames,
@@ -45,6 +49,14 @@ class MEDIA_EXPORT AudioRendererMixer
   void ProvideInput(const std::vector<float*>& audio_data,
                     int number_of_frames);
 
+  // Multiply each element of |src| (up to |len|) by |scale| and add to |dest|.
+  static void VectorFMAC(const float src[], float scale, int len, float dest[]);
+  static void VectorFMAC_C(const float src[], float scale, int len,
+                           float dest[]);
+  // SSE optimized VectorFMAC, requires |src|, |dest| to be 16-byte aligned.
+  static void VectorFMAC_SSE(const float src[], float scale, int len,
+                             float dest[]);
+
   // Output sink for this mixer.
   scoped_refptr<AudioRendererSink> audio_sink_;