Get access to EventBaseManager object

Summary: as title

Test Plan: run unit tests

Reviewed By: yfeldblum@fb.com

Subscribers: ming, fugalh, folly-diffs@, jsedgwick, yfeldblum, chalfant

FB internal diff: D1955074

folly/wangle/concurrent/IOThreadPoolExecutor.cpp

@@ -129,6 +129,10 @@ EventBase* IOThreadPoolExecutor::getEventBase(
   return nullptr;
 }
 
+EventBaseManager* IOThreadPoolExecutor::getEventBaseManager() {
+  return eventBaseManager_;
+}
+
 std::shared_ptr<ThreadPoolExecutor::Thread>
 IOThreadPoolExecutor::makeThread() {
   return std::make_shared<IOThread>(this);

folly/wangle/concurrent/IOThreadPoolExecutor.h

@@ -44,6 +44,8 @@ class IOThreadPoolExecutor : public ThreadPoolExecutor, public IOExecutor {
 
   static EventBase* getEventBase(ThreadPoolExecutor::ThreadHandle*);
 
+  EventBaseManager* getEventBaseManager();
+
  private:
   struct FOLLY_ALIGN_TO_AVOID_FALSE_SHARING IOThread : public Thread {
     IOThread(IOThreadPoolExecutor* pool)