Split rtc_task_queue target. Add separate target for sequenced_task_checker and weak_ptr.

webrtc/modules/video_coding/BUILD.gn

Index: webrtc/modules/video_coding/BUILD.gn
diff --git a/webrtc/modules/video_coding/BUILD.gn b/webrtc/modules/video_coding/BUILD.gn
index 4c283a86ed2773cc1698163a2e8190529dfa69ae..2148f8ac625b39ad84e6a3ab8df3bc22526183e4 100644
--- a/webrtc/modules/video_coding/BUILD.gn
+++ b/webrtc/modules/video_coding/BUILD.gn
@@ -101,6 +101,7 @@ rtc_static_library("video_coding") {
     "../../base:rtc_base_approved",
     "../../base:rtc_numerics",
     "../../base:rtc_task_queue",
+    "../../base:sequenced_task_checker",
     "../../common_video",
     "../../system_wrappers",
     "../rtp_rtcp:rtp_rtcp",
@@ -138,6 +139,7 @@ rtc_static_library("video_coding_utility") {
     "../../base:rtc_base_approved",
     "../../base:rtc_numerics",
     "../../base:rtc_task_queue",
+    "../../base:sequenced_task_checker",
     "../../common_video",
     "../../modules/rtp_rtcp:rtp_rtcp",
     "../../system_wrappers",
@@ -233,7 +235,7 @@ rtc_static_library("webrtc_vp8") {
     "../..:webrtc_common",
     "../../api/video_codecs:video_codecs_api",
     "../../base:rtc_base_approved",
-    "../../base:rtc_task_queue",
+    "../../base:sequenced_task_checker",
     "../../common_video",
     "../../system_wrappers",
   ]