add audio-buffer-size command line flag support to the input audio for all the platforms

media/audio/cras/audio_manager_cras.cc

Index: media/audio/cras/audio_manager_cras.cc
diff --git a/media/audio/cras/audio_manager_cras.cc b/media/audio/cras/audio_manager_cras.cc
index abc78dd4b78257c2602e31d2027472b94f5549c7..0d06fbe94be689362e2a4e033226be74b52a8861 100644
--- a/media/audio/cras/audio_manager_cras.cc
+++ b/media/audio/cras/audio_manager_cras.cc
@@ -37,9 +37,11 @@ static const int kMaxOutputStreams = 50;
 // Default sample rate for input and output streams.
 static const int kDefaultSampleRate = 48000;
 
-// Define bounds for the output buffer size.
+// Minimum bound for the output buffer size.
 static const int kMinimumOutputBufferSize = 512;
-static const int kMaximumOutputBufferSize = 8192;
+
+// Maximum bound for the input and output buffer size.
+static const int kMaximumBufferSize = 8192;
 
 // Default input buffer size.
 static const int kDefaultInputBufferSize = 1024;
@@ -75,17 +77,33 @@ void AudioManagerCras::GetAudioOutputDeviceNames(
   AddDefaultDevice(device_names);
 }
 
-AudioParameters AudioManagerCras::GetInputStreamParameters(
-    const std::string& device_id) {
+AudioParameters AudioManagerCras::GetPreferredInputStreamParameters(
+    const std::string& input_device_id,
+    const AudioParameters& input_params) {
+  ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
+  int sample_rate = kDefaultSampleRate;
+  int buffer_size = kDefaultInputBufferSize;
+  int bits_per_sample = 16;
+  int input_channels = 0;
+  if (input_params.IsValid()) {
+      sample_rate = input_params.sample_rate();
+      bits_per_sample = input_params.bits_per_sample();
+      channel_layout = input_params.channel_layout();
+      input_channels = input_params.input_channels();
+      buffer_size =
+          std::min(kMaximumBufferSize, input_params.frames_per_buffer());
+    }
+
   int user_buffer_size = GetUserBufferSize();
-  int buffer_size = user_buffer_size ?
-      user_buffer_size : kDefaultInputBufferSize;
+  if (user_buffer_size)
+    buffer_size = user_buffer_size;
+
 
   // TODO(hshi): Fine-tune audio parameters based on |device_id|. The optimal
   // parameters for the loopback stream may differ from the default.
   return AudioParameters(
-      AudioParameters::AUDIO_PCM_LOW_LATENCY, CHANNEL_LAYOUT_STEREO,
-      kDefaultSampleRate, 16, buffer_size);
+      AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
+      sample_rate, bits_per_sample, buffer_size);
 }
 
 AudioOutputStream* AudioManagerCras::MakeLinearOutputStream(