Support a user-provided string for the TLS ALPN extension.

Fix source formatting
Add TLS ALPN extension.

Bug: webrtc:8086
Change-Id: I1f28ccd78760d3415e465f734744d2c2f93845e2
Reviewed-on: https://chromium-review.googlesource.com/611150
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Justin Uberti <juberti@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Peter Thatcher <pthatcher@webrtc.org>
Commit-Queue: Diogo Real <diogor@google.com>
Cr-Commit-Position: refs/heads/master@{#19588}

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCIceServer.h

@@ -43,6 +43,9 @@ RTC_EXPORT
  */
 @property(nonatomic, readonly, nullable) NSString *hostname;
 
+/** List of protocols to be used in the TLS ALPN extension. */
+@property(nonatomic, readonly) NSArray<NSString *> *tlsAlpnProtocols;
+
 - (nonnull instancetype)init NS_UNAVAILABLE;
 
 /** Convenience initializer for a server with no authentication (e.g. STUN). */
@@ -73,7 +76,19 @@ RTC_EXPORT
                           username:(nullable NSString *)username
                         credential:(nullable NSString *)credential
                      tlsCertPolicy:(RTCTlsCertPolicy)tlsCertPolicy
-                          hostname:(nullable NSString *)hostname NS_DESIGNATED_INITIALIZER;
+                          hostname:(nullable NSString *)hostname;
+
+/**
+ * Initialize an RTCIceServer with its associated URLs, optional username,
+ * optional credential, TLS cert policy, hostname and ALPN protocols.
+ */
+- (instancetype)initWithURLStrings:(NSArray<NSString *> *)urlStrings
+                          username:(nullable NSString *)username
+                        credential:(nullable NSString *)credential
+                     tlsCertPolicy:(RTCTlsCertPolicy)tlsCertPolicy
+                          hostname:(nullable NSString *)hostname
+                  tlsAlpnProtocols:(NSArray<NSString *> *)tlsAlpnProtocols
+    NS_DESIGNATED_INITIALIZER;
 
 @end