Merge pull request #8118 from stanley-cheung/cpp-examples-missing-gpr-asserts

cpp examples missing gpr asserts

examples/cpp/helloworld/greeter_async_client.cc

@@ -36,6 +36,7 @@
 #include <string>
 
 #include <grpc++/grpc++.h>
+#include <grpc/support/log.h>
 
 #include "helloworld.grpc.pb.h"
 

examples/cpp/helloworld/greeter_async_client2.cc

@@ -36,6 +36,7 @@
 #include <string>
 
 #include <grpc++/grpc++.h>
+#include <grpc/support/log.h>
 #include <thread>
 
 #include "helloworld.grpc.pb.h"

examples/cpp/helloworld/greeter_async_server.cc

@@ -37,6 +37,7 @@
 #include <thread>
 
 #include <grpc++/grpc++.h>
+#include <grpc/support/log.h>
 
 #include "helloworld.grpc.pb.h"