Remove mediastreamsignaling from libjingle build files

+ Add deadbeef@ as owner.
+ Remove hellner@ as owner.

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjingle/source/talk/app/webrtc/mediastreamsignaling.h&l=28

Review URL: https://codereview.chromium.org/1460933003

Cr-Commit-Position: refs/heads/master@{#360574}

third_party/libjingle/BUILD.gn

@@ -323,8 +323,6 @@ if (enable_webrtc) {
       "source/talk/app/webrtc/mediastreaminterface.h",
       "source/talk/app/webrtc/mediastreamprovider.h",
       "source/talk/app/webrtc/mediastreamproxy.h",
-      "source/talk/app/webrtc/mediastreamsignaling.cc",
-      "source/talk/app/webrtc/mediastreamsignaling.h",
       "source/talk/app/webrtc/mediastreamtrack.h",
       "source/talk/app/webrtc/mediastreamtrackproxy.h",
       "source/talk/app/webrtc/notifier.h",

third_party/libjingle/OWNERS

 tommi@chromium.org
-hellner@chromium.org
+deadbeef@chromium.org
 kjellander@chromium.org
 sergeyu@chromium.org
-per-file README.chromium=*
\ No newline at end of file
+per-file README.chromium=*

third_party/libjingle/libjingle.gyp

@@ -282,8 +282,6 @@
             '<(libjingle_source)/talk/app/webrtc/mediastreaminterface.h',
             '<(libjingle_source)/talk/app/webrtc/mediastreamprovider.h',
             '<(libjingle_source)/talk/app/webrtc/mediastreamproxy.h',
-            '<(libjingle_source)/talk/app/webrtc/mediastreamsignaling.cc',
-            '<(libjingle_source)/talk/app/webrtc/mediastreamsignaling.h',
             '<(libjingle_source)/talk/app/webrtc/mediastreamtrack.h',
             '<(libjingle_source)/talk/app/webrtc/mediastreamtrackproxy.h',
             '<(libjingle_source)/talk/app/webrtc/notifier.h',