Improved error handling in AUAudioInputStream::Open() for Mac OSX

media/audio/mac/audio_low_latency_input_mac.cc

Index: media/audio/mac/audio_low_latency_input_mac.cc
diff --git a/media/audio/mac/audio_low_latency_input_mac.cc b/media/audio/mac/audio_low_latency_input_mac.cc
index afd17c90a9ae84e50553e2762853b9e36816ee36..c81c93da2d6bf016c07e56446e41b7cb4dab4440 100644
--- a/media/audio/mac/audio_low_latency_input_mac.cc
+++ b/media/audio/mac/audio_low_latency_input_mac.cc
@@ -114,13 +114,20 @@ AUAudioInputStream::~AUAudioInputStream() {
 bool AUAudioInputStream::Open() {
   DCHECK(thread_checker_.CalledOnValidThread());
   DVLOG(1) << "Open";
-  // Verify that we are not already opened.
-  if (audio_unit_)
+
+  // Verify that we are not already opened. Send appropriate error code to
+  // HandleError() to ensure that the error type is added to UMA stats where
+  // the frequency of error codes can be analyzed.
+  if (audio_unit_) {
+    HandleError(kAudioUnitErr_Initialized);

[tommi (sloooow) - chröme, 2016/02/05 12:29:30]

I'm not  sure this is a good idea.  HandleError() does more than just capture
the stats.  It actually fires an error which may close the stream.

For now though it makes sense to me to add a DCHECK at the beginning of this
function to catch programmer error:

DCHECK(!audio_unit_);

[henrika (OOO until Aug 14), 2016/02/05 12:50:51]

Done.

     return false;
+  }
 
-  // Verify that we have a valid device.
+  // Verify that we have a valid device. Send appropriate error code to
+  // HandleError() to ensure that the error type is added to UMA stats.
   if (input_device_id_ == kAudioObjectUnknown) {
     NOTREACHED() << "Device ID is unknown";
+    HandleError(kAudioUnitErr_InvalidElement);
     return false;
   }
 
@@ -136,6 +143,7 @@ bool AUAudioInputStream::Open() {
     UMA_HISTOGRAM_SPARSE_SLOWLY("Media.InputInvalidSampleRateMac", sample_rate);
     NOTREACHED() << "Requested sample-rate: " << format_.mSampleRate
                  << " must match the hardware sample-rate: " << sample_rate;
+    HandleError(kAudioUnitErr_InvalidParameter);

[henrika (OOO until Aug 14), 2016/02/05 12:16:28]

Adding one extra here since we can then see the relation (frequency) of this
error in relation to the others.

[tommi (sloooow) - chröme, 2016/02/05 12:29:30]

Acknowledged.

     return false;
   }
 
@@ -154,8 +162,13 @@ bool AUAudioInputStream::Open() {
       0
   };
 
+  // Find a component that meets the description in |desc|.
   AudioComponent comp = AudioComponentFindNext(nullptr, &desc);
   DCHECK(comp);
+  if (!comp) {
+    HandleError(kAudioComponentErr_InstanceInvalidated);
+    return false;
+  }
 
   // Get access to the service provided by the specified Audio Unit.
   OSStatus result = AudioComponentInstanceNew(comp, &audio_unit_);