Improve testing of SRTP external auth code paths.

webrtc/pc/srtpfilter.h

Index: webrtc/pc/srtpfilter.h
diff --git a/webrtc/pc/srtpfilter.h b/webrtc/pc/srtpfilter.h
index 46b9dea19f38400abdb38f56cabc2eeece1197fb..3df787646c740eb819f93986e697de0daabf1237 100644
--- a/webrtc/pc/srtpfilter.h
+++ b/webrtc/pc/srtpfilter.h
@@ -114,12 +114,18 @@ class SrtpFilter {
   // Returns srtp overhead for rtp packets.
   bool GetSrtpOverhead(int* srtp_overhead) const;
 
-#if defined(ENABLE_EXTERNAL_AUTH)
+  // If external auth is enabled, SRTP will write a dummy auth tag that then
+  // later must get replaced before the packet is sent out. Only supported for
+  // non-GCM cipher suites and can be checked through "IsExternalAuthActive"
+  // if it is actually used. This method is only valid before the RTP params
+  // have been set.
+  void EnableExternalAuth();
+  bool IsExternalAuthEnabled() const;
+
   // A SRTP filter supports external creation of the auth tag if a non-GCM
   // cipher is used. This method is only valid after the RTP params have
   // been set.
   bool IsExternalAuthActive() const;
-#endif
 
   // Update the silent threshold (in ms) for signaling errors.
   void set_signal_silent_time(int signal_silent_time_in_ms);
@@ -169,8 +175,9 @@ class SrtpFilter {
     // ST_INIT.
     ST_RECEIVEDPRANSWER
   };
-  State state_;
-  int signal_silent_time_in_ms_;
+  State state_ = ST_INIT;
+  int signal_silent_time_in_ms_ = 0;
+  bool external_auth_enabled_ = false;
   std::vector<CryptoParams> offer_params_;
   std::unique_ptr<SrtpSession> send_session_;
   std::unique_ptr<SrtpSession> recv_session_;
@@ -213,12 +220,18 @@ class SrtpSession {
 
   int GetSrtpOverhead() const;
 
-#if defined(ENABLE_EXTERNAL_AUTH)
+  // If external auth is enabled, SRTP will write a dummy auth tag that then
+  // later must get replaced before the packet is sent out. Only supported for
+  // non-GCM cipher suites and can be checked through "IsExternalAuthActive"
+  // if it is actually used. This method is only valid before the RTP params
+  // have been set.
+  void EnableExternalAuth();
+  bool IsExternalAuthEnabled() const;
+
   // A SRTP session supports external creation of the auth tag if a non-GCM
   // cipher is used. This method is only valid after the RTP params have
   // been set.
   bool IsExternalAuthActive() const;
-#endif
 
   // Update the silent threshold (in ms) for signaling errors.
   void set_signal_silent_time(int signal_silent_time_in_ms);
@@ -246,9 +259,8 @@ class SrtpSession {
   static bool inited_;
   static rtc::GlobalLockPod lock_;
   int last_send_seq_num_ = -1;
-#if defined(ENABLE_EXTERNAL_AUTH)
   bool external_auth_active_ = false;
-#endif
+  bool external_auth_enabled_ = false;
   RTC_DISALLOW_COPY_AND_ASSIGN(SrtpSession);
 };