Add base class abstract macro to all classes

src/core/lib/iomgr/executor/mpmcqueue.h

@@ -48,6 +48,8 @@ class MPMCQueueInterface {
 
   // Return number of elements in the queue currently
   virtual int count() const  GRPC_ABSTRACT;
+
+  GRPC_ABSTRACT_BASE_CLASS
 };
 
 class MPMCQueue : public MPMCQueueInterface {

test/core/iomgr/mpmcqueue_test.cc

@@ -141,6 +141,8 @@ class WorkThread {
   void Start() { thd_.Start(); }
   void Join() { thd_.Join(); }
 
+  GRPC_ABSTRACT_BASE_CLASS
+
  private:
   void Run() {
     items_ = new WorkItem*[num_items_];