Allow construction of TaskQueueForTest with TaskQueueBase

Bug: webrtc:10365
Change-Id: I1f19cdc2032e57bb552a98cb9fb8dc03282713bf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/127892
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27220}

rtc_base/task_queue_for_test.h

@@ -24,6 +24,7 @@ namespace webrtc {
 
 class RTC_LOCKABLE TaskQueueForTest : public rtc::TaskQueue {
  public:
+  using rtc::TaskQueue::TaskQueue;
   explicit TaskQueueForTest(absl::string_view name = "TestQueue",
                             Priority priority = Priority::NORMAL);
   TaskQueueForTest(const TaskQueueForTest&) = delete;