Add the new files from https://webrtc-codereview.appspot.com/37889004/ to libjingle.gyp

BUG=webrtc:4241

Review URL: https://codereview.chromium.org/943033004

Cr-Commit-Position: refs/heads/master@{#317604}

third_party/libjingle/libjingle.gyp

@@ -346,6 +346,10 @@
             '<(libjingle_source)/talk/app/webrtc/audiotrackrenderer.h',
             '<(libjingle_source)/talk/app/webrtc/datachannel.cc',
             '<(libjingle_source)/talk/app/webrtc/datachannel.h',
+            '<(libjingle_source)/talk/app/webrtc/dtlsidentityservice.cc',
+            '<(libjingle_source)/talk/app/webrtc/dtlsidentityservice.h',
+            '<(libjingle_source)/talk/app/webrtc/dtlsidentitystore.cc',
+            '<(libjingle_source)/talk/app/webrtc/dtlsidentitystore.h',
             '<(libjingle_source)/talk/app/webrtc/dtmfsender.cc',
             '<(libjingle_source)/talk/app/webrtc/dtmfsender.h',
             '<(libjingle_source)/talk/app/webrtc/jsep.h',