Add commandline flag to enable GCM cipher suites from RFC 7714 in WebRTC.

content/renderer/media/webrtc/peer_connection_dependency_factory.cc

Index: content/renderer/media/webrtc/peer_connection_dependency_factory.cc
diff --git a/content/renderer/media/webrtc/peer_connection_dependency_factory.cc b/content/renderer/media/webrtc/peer_connection_dependency_factory.cc
index 6789d07251609ff3b21780dfc7632d7e9d8095f6..82033935e1dae07917f5e1570158f629dad021b0 100644
--- a/content/renderer/media/webrtc/peer_connection_dependency_factory.cc
+++ b/content/renderer/media/webrtc/peer_connection_dependency_factory.cc
@@ -261,7 +261,8 @@ void PeerConnectionDependencyFactory::InitializeSignalingThread(
   factory_options.disable_sctp_data_channels = false;
   factory_options.disable_encryption =
       cmd_line->HasSwitch(switches::kDisableWebRtcEncryption);
-
+  factory_options.crypto_options.enable_gcm_crypto_suites =
+      cmd_line->HasSwitch(switches::kEnableWebRtcSrtpAesGcm);
   pc_factory_->SetOptions(factory_options);
 
   event->Signal();