Improved error handling in iOS ADM to avoid race during init

webrtc/modules/audio_device/ios/audio_device_ios.h

Index: webrtc/modules/audio_device/ios/audio_device_ios.h
diff --git a/webrtc/modules/audio_device/ios/audio_device_ios.h b/webrtc/modules/audio_device/ios/audio_device_ios.h
index 8f8ba0a9c53ce7c6cd059885f3e241829bf01dea..3061aef9f77faf791a38ba93effb47f7d23a0e7b 100644
--- a/webrtc/modules/audio_device/ios/audio_device_ios.h
+++ b/webrtc/modules/audio_device/ios/audio_device_ios.h
@@ -13,6 +13,7 @@
 
 #include <AudioUnit/AudioUnit.h>
 
+#include "webrtc/base/criticalsection.h"
 #include "webrtc/base/scoped_ptr.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/modules/audio_device/audio_device_generic.h"
@@ -184,6 +185,9 @@ class AudioDeviceIOS : public AudioDeviceGeneric {
   // Closes and deletes the voice-processing I/O unit.
   bool ShutdownPlayOrRecord();
 
+  // Helper method for destroying the existing audio unit.
+  void DisposeAudioUnit();
+
   // Callback function called on a real-time priority I/O thread from the audio
   // unit. This method is used to signal that recorded audio is available.
   static OSStatus RecordedDataIsAvailable(
@@ -211,6 +215,16 @@ class AudioDeviceIOS : public AudioDeviceGeneric {
                             UInt32 in_number_frames,
                             AudioBufferList* io_data);
 
+  // Counts number of times setActive:YES has been called on the singleton
+  // AVAudioSession instance. Used to ensure that we don't disable an audio
+  // session when it is still in used by other instances of this object.
+  // Member is static to ensure that the value is counted for all instances
+  // and not per instance.
+  static int audio_session_activation_count_;

[pbos-webrtc, 2015/11/18 12:54:22]

Put GUARDED_BY(lock_) between "count_" and ";"

[henrika_webrtc, 2015/11/18 16:05:32]

Done.

+
+  // Protects |audio_session_activation_count_|.
+  static rtc::GlobalLockPod lock_;
+
   // Ensures that methods are called from the same thread as this object is
   // created on.
   rtc::ThreadChecker thread_checker_;