Check the mic volume only periodically on Mac.

webrtc/modules/audio_device/mac/audio_device_mac.cc

Index: webrtc/modules/audio_device/mac/audio_device_mac.cc
diff --git a/webrtc/modules/audio_device/mac/audio_device_mac.cc b/webrtc/modules/audio_device/mac/audio_device_mac.cc
index 3449188dc0c9bf9b90b9a285ab44e6b675a18def..d963f2b7f2a65503bce08ff238c7df4b0ef57609 100644
--- a/webrtc/modules/audio_device/mac/audio_device_mac.cc
+++ b/webrtc/modules/audio_device/mac/audio_device_mac.cc
@@ -149,7 +149,8 @@ AudioDeviceMac::AudioDeviceMac(const int32_t id) :
     _paRenderBuffer(NULL),
     _captureBufSizeSamples(0),
     _renderBufSizeSamples(0),
-    prev_key_state_()
+    prev_key_state_(),
+    get_mic_volume_counter_ms_(0)
 {
     WEBRTC_TRACE(kTraceMemory, kTraceAudioDevice, id,
                  "%s created", __FUNCTION__);
@@ -379,6 +380,8 @@ int32_t AudioDeviceMac::Init()
     _recWarning = 0;
     _recError = 0;
 
+    get_mic_volume_counter_ms_ = 0;
+
     _initialized = true;
 
     return 0;
@@ -3181,12 +3184,17 @@ bool AudioDeviceMac::CaptureWorkerThread()
 
         if (AGC())
         {
-            // store current mic level in the audio buffer if AGC is enabled
-            if (MicrophoneVolume(currentMicLevel) == 0)
-            {
-                // this call does not affect the actual microphone volume
-                _ptrAudioBuffer->SetCurrentMicLevel(currentMicLevel);
+            // Use mod to ensure we check the volume on the first pass.

[henrika_webrtc, 2016/01/08 08:14:42]

Out indentation kind of sucks but I guess we should change it in the complete
file and not just where we make changes. Just an idea.

[Andrew MacDonald, 2016/01/08 08:22:09]

:)

I can run clang-format on these files in a follow-up CL.

+            if (get_mic_volume_counter_ms_ % kGetMicVolumeIntervalMs == 0) {
+                get_mic_volume_counter_ms_ = 0;
+                // store current mic level in the audio buffer if AGC is enabled
+                if (MicrophoneVolume(currentMicLevel) == 0)
+                {
+                    // this call does not affect the actual microphone volume
+                    _ptrAudioBuffer->SetCurrentMicLevel(currentMicLevel);
+                }
             }
+            get_mic_volume_counter_ms_ += kBufferSizeMs;
         }
 
         _ptrAudioBuffer->SetVQEData(msecOnPlaySide, msecOnRecordSide, 0);