Added option to shutdown Scheduler before destruction.

PiperOrigin-RevId: 248384183

Author: smiles

app/src/scheduler.cc

@@ -72,9 +72,14 @@ Scheduler::Scheduler()
 }
 
 Scheduler::~Scheduler() {
+  CancelAllAndShutdownWorkerThread();
+}
+
+void Scheduler::CancelAllAndShutdownWorkerThread() {
   {
-    // Notify the worker thread to stop processing anymore request
+    // Notify the worker thread to stop processing anymore requests.
     MutexLock lock(request_mutex_);
+    if (terminating_) return;
     terminating_ = true;
   }
 

app/src/scheduler.h

@@ -123,6 +123,9 @@ class Scheduler {
                           ScheduleTimeMs delay = 0, ScheduleTimeMs repeat = 0);
 #endif  // FIREBASE_USE_STD_FUNCTION
 
+  // Cancel all scheduled callbacks and shut down the worker thread.
+  void CancelAllAndShutdownWorkerThread();
+
  private:
   typedef uint64_t RequestId;
   // The request data for all scheduled callback.