Fix missing build dependency for third_party/webrtc_overrides/task_queue

TBR=tommi

Bug: None
Change-Id: I58f12bcc2deb794f921ad3dd94d527fabe8e7681
Reviewed-on: https://chromium-review.googlesource.com/970462Reviewed-by: Magnus Jedvert <magjed@chromium.org>
Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Magnus Jedvert <magjed@chromium.org>
Commit-Queue: Tommi <tommi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544329}

third_party/webrtc_overrides/BUILD.gn

@@ -143,6 +143,7 @@ source_set("task_queue_impl") {
     "rtc_base/task_queue.cc",
   ]
   deps = [
+    "//base",
     "//third_party/webrtc/rtc_base:rtc_task_queue_api",
   ]
 }