Add rtc_base:async_resolver to WebRTC component.

Bug: webrtc:9987
Change-Id: Iae028ac321bffb9c7b0980dd4323fe5d81d5b66f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593088Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837466}

third_party/webrtc_overrides/BUILD.gn

@@ -78,6 +78,7 @@ component("webrtc_component") {
     "//third_party/webrtc/pc:rtc_pc_base",
     "//third_party/webrtc/rtc_base",
     "//third_party/webrtc/rtc_base:async_resolver_interface",
+    "//third_party/webrtc/rtc_base:async_resolver",
     "//third_party/webrtc/rtc_base:ip_address",
     "//third_party/webrtc/rtc_base:rtc_base",
     "//third_party/webrtc/rtc_base:rtc_base_approved",