Get PulseAudio implementation working.

media/base/audio_bus.h

Index: media/base/audio_bus.h
diff --git a/media/base/audio_bus.h b/media/base/audio_bus.h
index 49bed82e904b8b32384091cf053d0ee9b1cbe888..5ea4e08529800346d0dae77a19c322238f3d2d5d 100644
--- a/media/base/audio_bus.h
+++ b/media/base/audio_bus.h
@@ -62,6 +62,8 @@ class MEDIA_EXPORT AudioBus {
   // any unfilled frames when |frames| is less than frames().
   void FromInterleaved(const void* source, int frames, int bytes_per_sample);
   void ToInterleaved(int frames, int bytes_per_sample, void* dest) const;
+  void ToInterleavedPartial(int start_frame, int frames, int bytes_per_sample,
+                            void* dest) const;
 
   // Similar to FromInterleaved() above, but meant for streaming sources.  Does
   // not zero out remaining frames, the caller is responsible for doing so using