Support delayed AudioUnit initialization.

webrtc/modules/audio_device/ios/voice_processing_audio_unit.h

Index: webrtc/modules/audio_device/ios/voice_processing_audio_unit.h
diff --git a/webrtc/modules/audio_device/ios/voice_processing_audio_unit.h b/webrtc/modules/audio_device/ios/voice_processing_audio_unit.h
index c1e5cafb4bbc9500c70c172b9a21064217ddb4c5..2f881e77fcdcbb963a95e0a75846cd8bc807090b 100644
--- a/webrtc/modules/audio_device/ios/voice_processing_audio_unit.h
+++ b/webrtc/modules/audio_device/ios/voice_processing_audio_unit.h
@@ -49,6 +49,16 @@ class VoiceProcessingAudioUnit {
   ~VoiceProcessingAudioUnit();
 
   // TODO(tkchin): enum for state and state checking.
+  enum State : int32_t {
+    // Init() should be called.
+    kInitRequired,
+    // Audio unit created but not initialized.
+    kUninitialized,
+    // Initialized but not started. Equivalent to stopped.
+    kInitialized,
+    // Initialized and started.
+    kStarted,
+  };
 
   // Number of bytes per audio sample for 16-bit signed integer representation.
   static const UInt32 kBytesPerSample;
@@ -60,6 +70,8 @@ class VoiceProcessingAudioUnit {
   // Does not intialize the audio unit.
   bool Init();
 
+  VoiceProcessingAudioUnit::State GetState() const;
+
   // Initializes the underlying audio unit with the given sample rate.
   bool Initialize(Float64 sample_rate);
 
@@ -118,6 +130,7 @@ class VoiceProcessingAudioUnit {
 
   VoiceProcessingAudioUnitObserver* observer_;
   AudioUnit vpio_unit_;
+  VoiceProcessingAudioUnit::State state_;
 };
 }  // namespace webrtc