Revert of Remove the last piece of deprecated synchronous IO code.

media/audio/cras/cras_unified.h

Index: media/audio/cras/cras_unified.h
diff --git a/media/audio/cras/cras_unified.h b/media/audio/cras/cras_unified.h
index 7e946e0f3a2ba23096c1c2feaafd739fd931aad2..db1d9feb648e3c0d2c606f9ab3dbe3474e8940a2 100644
--- a/media/audio/cras/cras_unified.h
+++ b/media/audio/cras/cras_unified.h
@@ -70,6 +70,13 @@
                           const timespec* input_ts,
                           const timespec* output_ts);
 
+  // Receives input samples and write output samples for a unified I/O stream.
+  uint32 ReadWriteAudio(size_t frames,
+                        uint8* input_samples,
+                        uint8* output_samples,
+                        const timespec* input_ts,
+                        const timespec* output_ts);
+
   // Writes audio for a playback stream.
   uint32 WriteAudio(size_t frames, uint8* buffer, const timespec* sample_ts);
 
@@ -101,6 +108,7 @@
   AudioSourceCallback* source_callback_;
 
   // Container for exchanging data with AudioSourceCallback::OnMoreData().
+  scoped_ptr<AudioBus> input_bus_;
   scoped_ptr<AudioBus> output_bus_;
 
   // Direciton of the stream.