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

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
diff --git a/media/audio/mac/audio_manager_mac.cc b/media/audio/mac/audio_manager_mac.cc
index 970720679abf418b9cd2ef11f49d017d75c60084..71af5e654966b788649cf6aaa8e88c0d2cd4e6c2 100644
--- a/media/audio/mac/audio_manager_mac.cc
+++ b/media/audio/mac/audio_manager_mac.cc
@@ -432,8 +432,9 @@ void AudioManagerMac::GetAudioOutputDeviceNames(
   GetAudioDeviceInfo(false, device_names);
 }
 
-AudioParameters AudioManagerMac::GetInputStreamParameters(
-    const std::string& device_id) {
+AudioParameters AudioManagerMac::GetPreferredInputStreamParameters(
+    const std::string& input_device_id,
+    const AudioParameters& input_params) {
   AudioDeviceID device = GetAudioDeviceIdByUId(true, device_id);
   if (device == kAudioObjectUnknown) {
     DLOG(ERROR) << "Invalid device " << device_id;
@@ -442,29 +443,41 @@ AudioParameters AudioManagerMac::GetInputStreamParameters(
         kFallbackSampleRate, 16, ChooseBufferSize(kFallbackSampleRate));
   }
 
+  const bool has_valid_input_params = input_params.IsValid();
+
   int channels = 0;
-  ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
+  ChannelLayout channel_layout = has_valid_input_params ?
+      input_params.channel_layout() : CHANNEL_LAYOUT_STEREO;
   if (GetDeviceChannels(device, kAudioDevicePropertyScopeInput, &channels) &&
       channels <= 2) {
+    // Use the native channel layout of the device.
     channel_layout = GuessChannelLayout(channels);
   } else {
     DLOG(ERROR) << "Failed to get the device channels, use stereo as default "
                 << "for device " << device_id;
   }
 
+  // Use the native sample rate of the device if it can.
   int sample_rate = HardwareSampleRateForDevice(device);
-  if (!sample_rate)
-    sample_rate = kFallbackSampleRate;
+  if (!sample_rate) {
+    sample_rate = has_valid_input_params ?
+        input_params.sample_rate() : kFallbackSampleRate;
+  }
+
+  int buffer_size = ChooseBufferSize(sample_rate);
+
+  if (has_valid_input_params) {
+    buffer_size =
+        std::min(kMaximumInputOutputBufferSize,
+                 std::max(input_params.frames_per_buffer(), buffer_size));
+  }
 
-  // Due to the sharing of the input and output buffer sizes, we need to choose
-  // the input buffer size based on the output sample rate.  See
-  // http://crbug.com/154352.
-  const int buffer_size = ChooseBufferSize(sample_rate);
+  const int bits_per_sample = has_valid_input_params ?
+      input_params.bits_per_sample() : 16;
 
-  // TODO(xians): query the native channel layout for the specific device.
   return AudioParameters(
       AudioParameters::AUDIO_PCM_LOW_LATENCY, channel_layout,
-      sample_rate, 16, buffer_size);
+      sample_rate, bits_per_sample, buffer_size);
 }
 
 std::string AudioManagerMac::GetAssociatedOutputDeviceID(