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

media/audio/audio_parameters.h

Index: media/audio/audio_parameters.h
diff --git a/media/audio/audio_parameters.h b/media/audio/audio_parameters.h
index 03fe043dfadd53e4ae4bf75edc1e9ce5eeadcacf..b23d26fdcae0e9ff57f310a826348cfea2a11a39 100644
--- a/media/audio/audio_parameters.h
+++ b/media/audio/audio_parameters.h
@@ -58,14 +58,17 @@
                   int sample_rate, int bits_per_sample,
                   int frames_per_buffer);
   AudioParameters(Format format, ChannelLayout channel_layout,
+                  int input_channels,
                   int sample_rate, int bits_per_sample,
                   int frames_per_buffer, int effects);
   AudioParameters(Format format, ChannelLayout channel_layout,
-                  int channels, int sample_rate, int bits_per_sample,
+                  int channels, int input_channels,
+                  int sample_rate, int bits_per_sample,
                   int frames_per_buffer, int effects);
 
   void Reset(Format format, ChannelLayout channel_layout,
-             int channels, int sample_rate, int bits_per_sample,
+             int channels, int input_channels,
+             int sample_rate, int bits_per_sample,
              int frames_per_buffer);
 
   // Checks that all values are in the expected range. All limits are specified
@@ -91,6 +94,7 @@
   int bits_per_sample() const { return bits_per_sample_; }
   int frames_per_buffer() const { return frames_per_buffer_; }
   int channels() const { return channels_; }
+  int input_channels() const { return input_channels_; }
   int effects() const { return effects_; }
 
   // Comparison with other AudioParams.
@@ -99,6 +103,7 @@
            sample_rate_ == other.sample_rate() &&
            channel_layout_ == other.channel_layout() &&
            channels_ == other.channels() &&
+           input_channels_ == other.input_channels() &&
            bits_per_sample_ == other.bits_per_sample() &&
            frames_per_buffer_ == other.frames_per_buffer() &&
            effects_ == other.effects();
@@ -115,6 +120,9 @@
 
   int channels_;                  // Number of channels. Value set based on
                                   // |channel_layout|.
+  int input_channels_;            // Optional number of input channels.
+                                  // Normally 0, but can be set to specify
+                                  // synchronized I/O.
   int effects_;                   // Bitmask using PlatformEffectsMask.
 };
 
@@ -124,6 +132,8 @@
     return a.format() < b.format();
   if (a.channels() != b.channels())
     return a.channels() < b.channels();
+  if (a.input_channels() != b.input_channels())
+    return a.input_channels() < b.input_channels();
   if (a.sample_rate() != b.sample_rate())
     return a.sample_rate() < b.sample_rate();
   if (a.bits_per_sample() != b.bits_per_sample())