Fix some TODO(GYP) in the GN build.

third_party/libjingle/BUILD.gn

Index: third_party/libjingle/BUILD.gn
diff --git a/third_party/libjingle/BUILD.gn b/third_party/libjingle/BUILD.gn
index 8c6acfdd82df1b5228b18a05afca3eb1c558c423..c019fa553d0ec398cfa614d47a0f81021510cfd1 100644
--- a/third_party/libjingle/BUILD.gn
+++ b/third_party/libjingle/BUILD.gn
@@ -54,7 +54,6 @@ config("jingle_public_configs") {
     "NO_SOUND_SYSTEM",
   ]
 
-  # TODO(GYP): Port is_win blocks.
   if (is_linux) {
     defines += [
       "LINUX",
@@ -83,17 +82,6 @@ config("jingle_public_configs") {
   if (is_posix) {
     defines += [ "WEBRTC_POSIX" ]
   }
-
-  # TODO(GYP): Support these in GN.
-  # if (is_bsd) {
-  #   defines += [ "BSD" ]
-  # }
-  # if (is_openbsd) {
-  #   defines += [ "OPENBSD" ]
-  # }
-  # if (is_freebsd) {
-  #   defines += [ "FREEBSD" ]
-  # }
   if (is_chromeos) {
     defines += [ "CHROMEOS" ]
   }
@@ -436,4 +424,3 @@ if (enable_webrtc) {
     ]
   }
 }  # enable_webrtc
-# TODO(GYP): Port libjingle.gyp's enable_webrtc condition block.