Bug 1530715 - P12: Remove the unused variable in AudioUnitStream. r=padenot

Removing expected_output_callbacks_in_a_row since it is not being used.

Differential Revision: https://phabricator.services.mozilla.com/D34045

--HG--
extra : moz-landing-system : lando

media/libcubeb/cubeb-coreaudio-rs/README_MOZILLA

@@ -3,4 +3,4 @@ git repository using the update.sh script.
 
 The cubeb-coreaudio-rs git repository is: https://github.com/ChunMinChang/cubeb-coreaudio-rs
 
-The git commit ID used was 98f1c507e678a76aa19fe1cfeb532cd68455a712 (2019-06-21 14:26:53 -0700)
+The git commit ID used was 90294adec824902d43e188db04b2752b0a2faa9b (2019-06-21 14:34:58 -0700)

media/libcubeb/cubeb-coreaudio-rs/src/backend/mod.rs

@@ -2791,8 +2791,6 @@ struct AudioUnitStream<'ctx> {
     // I/O device sample rate
     input_hw_rate: f64,
     output_hw_rate: f64,
-    // Expected I/O thread interleave, calculated from I/O hw rate.
-    expected_output_callbacks_in_a_row: i32,
     mutex: OwnedCriticalSection,
     // Hold the input samples in every input callback iteration.
     // Only accessed on input/output callback thread and during initial configure.
@@ -2870,7 +2868,6 @@ impl<'ctx> AudioUnitStream<'ctx> {
             output_unit: ptr::null_mut(),
             input_hw_rate: 0_f64,
             output_hw_rate: 0_f64,
-            expected_output_callbacks_in_a_row: 0,
             mutex: OwnedCriticalSection::new(),
             input_linear_buffer: None,
             frames_played: AtomicU64::new(0),
@@ -4202,14 +4199,6 @@ impl<'ctx> AudioUnitStream<'ctx> {
             }
         }
 
-        if !self.input_unit.is_null() && !self.output_unit.is_null() {
-            // According to the I/O hardware rate it is expected a specific pattern of callbacks
-            // for example is input is 44100 and output is 48000 we expected no more than 2
-            // out callback in a row.
-            self.expected_output_callbacks_in_a_row =
-                (self.output_hw_rate / self.input_hw_rate).ceil() as i32
-        }
-
         if self.install_device_changed_callback().is_err() {
             cubeb_log!(
                 "({:p}) Could not install all device change callback.",