Return error in case chaining fails

Author: deepikabhavnani

events/EventQueue.cpp

@@ -16,7 +16,6 @@
  */
 #include "events/EventQueue.h"
 #include "events/mbed_events.h"
-#include "platform/mbed_assert.h"
 
 using mbed::Callback;
 
@@ -72,12 +71,12 @@ void EventQueue::background(Callback<void(int)> update)
     }
 }
 
-void EventQueue::chain(EventQueue *target)
+int EventQueue::chain(EventQueue *target)
 {
     if (target) {
-        MBED_ASSERT(equeue_chain(&_equeue, &target->_equeue) == 0);
+        return equeue_chain(&_equeue, &target->_equeue);
     } else {
-        MBED_ASSERT(equeue_chain(&_equeue, 0) == 0);
+        return equeue_chain(&_equeue, 0);
     }
 }
 }

events/EventQueue.h

@@ -181,8 +181,11 @@ class EventQueue : private mbed::NonCopyable<EventQueue> {
      *
      *  @param target   Queue that will dispatch this queue's events as a
      *                  part of its dispatch loop
+     *
+     *  @return Zero on success and negative error code value if chaining fails
+     *
      */
-    void chain(EventQueue *target);
+    int chain(EventQueue *target);