message: Add RTC_EXPORT to CurrentTaskQueueSetter
  This allows for its use in test targets in Chromium Windows, which fixes
  the compiled errors found in
  Cr-Commit-Position: refs/heads/main@{#36939}
diff: @@ -130,7 +130,7 @@ class RTC_LOCKABLE RTC_EXPORT TaskQueueBase {
  bool IsCurrent() const { return Current() == this; }
  protected:
  - class CurrentTaskQueueSetter {
  + class RTC_EXPORT CurrentTaskQueueSetter {
  public:
  explicit CurrentTaskQueueSetter(TaskQueueBase* task_queue);
  CurrentTaskQueueSetter(const CurrentTaskQueueSetter&) = delete;
  