Break out pc/session_description build target (part 2)

Move the files.

Bug: webrtc:11967
Change-Id: Ib8c26e32248064ce6140bef79410e5a4a595d01e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/221861
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34266}
diff --git a/pc/BUILD.gn b/pc/BUILD.gn
index 727f30e..e4e6dda 100644
--- a/pc/BUILD.gn
+++ b/pc/BUILD.gn
@@ -81,16 +81,6 @@
     "sctp_transport.h",
     "sctp_utils.cc",
     "sctp_utils.h",
-
-    # Will move to "session_description" target
-    # when downstream projects depend on that.
-    "session_description.cc",
-    "session_description.h",
-
-    # Will move to "simulcast_description" target
-    # when downstream projects depend on that.
-    "simulcast_description.cc",
-    "simulcast_description.h",
     "srtp_filter.cc",
     "srtp_filter.h",
     "srtp_session.cc",
@@ -187,9 +177,8 @@
 rtc_source_set("session_description") {
   visibility = [ "*" ]
   sources = [
-    # Future home of
-    #"session_description.cc",
-    #"session_description.h",
+    "session_description.cc",
+    "session_description.h",
   ]
   deps = [
     ":media_protocol_names",
@@ -212,9 +201,8 @@
 rtc_source_set("simulcast_description") {
   visibility = [ "*" ]
   sources = [
-    # Future home of
-    # "simulcast_description.cc",
-    # "simulcast_description.h",
+    "simulcast_description.cc",
+    "simulcast_description.h",
   ]
   deps = [
     "../rtc_base:checks",