Support delayed AudioUnit initialization.

webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h

Index: webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h
diff --git a/webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h b/webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h
index 43af7c86e2fa202bbf2a6e20d6fc47673e1102d4..c6738e7a033ccd9856e67c01a941ce20ff157863 100644
--- a/webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h
+++ b/webrtc/modules/audio_device/ios/objc/RTCAudioSession+Private.h
@@ -14,12 +14,25 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+@class RTCAudioSessionConfiguration;
+
 @interface RTCAudioSession ()
 
 /** Number of times setActive:YES has succeeded without a balanced call to
  *  setActive:NO.
  */
-@property(nonatomic, readonly) NSInteger activationCount;
+@property(nonatomic, readonly) int activationCount;
+
+/** The number of times |beginWebRTCSession| was called without a balanced call
+ *  to |endWebRTCSession|.
+ */
+@property(nonatomic, readonly) int webRTCSessionCount;
+
+/** The configuration of the audio session before configureWebRTCSession
+ *  was first called.
+ */
+@property(nonatomic, strong, nullable)
+    RTCAudioSessionConfiguration *savedConfiguration;
 
 - (BOOL)checkLock:(NSError **)outError;
 
@@ -29,9 +42,26 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)pushDelegate:(id<RTCAudioSessionDelegate>)delegate;
 
+/** Signals RTCAudioSession that a WebRTC session is about to begin and
+ *  audio configuration is needed. Will configure the audio session for WebRTC
+ *  if not already configured and if configuration is not delayed.
+ *  Successful calls must be balanced by a call to endWebRTCSession.
+ */
+- (BOOL)beginWebRTCSession:(NSError **)outError;
+
+/** Signals RTCAudioSession that a WebRTC session is about to end and audio
+ *  unconfiguration is needed. Will unconfigure the audio session for WebRTC
+ *  if this is the last unmatched call and if configuration is not delayed.
+ */
+- (BOOL)endWebRTCSession:(NSError **)outError;
+
+/** Returns a configuration error with the given description. */
+- (NSError *)configurationErrorWithDescription:(NSString *)description;
+
 // Properties and methods for tests.
 @property(nonatomic, readonly)
     std::vector<__weak id<RTCAudioSessionDelegate> > delegates;
+
 - (void)notifyDidBeginInterruption;
 - (void)notifyDidEndInterruptionWithShouldResumeSession:
     (BOOL)shouldResumeSession;
@@ -39,6 +69,10 @@ NS_ASSUME_NONNULL_BEGIN
     previousRoute:(AVAudioSessionRouteDescription *)previousRoute;
 - (void)notifyMediaServicesWereLost;
 - (void)notifyMediaServicesWereReset;
+- (void)notifyShouldConfigure;
+- (void)notifyShouldUnconfigure;
+- (void)notifyDidConfigure;
+- (void)notifyDidUnconfigure;
 
 @end