Fix Android build issues and gRPC LB policy

src/core/plugin_registry/grpc_unsecure_plugin_registry.c

 /*
  *
  * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 25 matching lines @@
 extern void grpc_chttp2_plugin_init(void);
 extern void grpc_chttp2_plugin_shutdown(void);
 extern void grpc_client_config_init(void);
 extern void grpc_client_config_shutdown(void);
 extern void grpc_resolver_dns_native_init(void);
 extern void grpc_resolver_dns_native_shutdown(void);
 extern void grpc_resolver_sockaddr_init(void);
 extern void grpc_resolver_sockaddr_shutdown(void);
 extern void grpc_load_reporting_plugin_init(void);
 extern void grpc_load_reporting_plugin_shutdown(void);
-extern void grpc_lb_policy_grpclb_init(void);
-extern void grpc_lb_policy_grpclb_shutdown(void);
 extern void grpc_lb_policy_pick_first_init(void);
 extern void grpc_lb_policy_pick_first_shutdown(void);
 extern void grpc_lb_policy_round_robin_init(void);
 extern void grpc_lb_policy_round_robin_shutdown(void);
-extern void census_grpc_plugin_init(void);
-extern void census_grpc_plugin_shutdown(void);
 
 void grpc_register_built_in_plugins(void) {
   grpc_register_plugin(grpc_chttp2_plugin_init,
                        grpc_chttp2_plugin_shutdown);
   grpc_register_plugin(grpc_client_config_init,
                        grpc_client_config_shutdown);
   grpc_register_plugin(grpc_resolver_dns_native_init,
                        grpc_resolver_dns_native_shutdown);
   grpc_register_plugin(grpc_resolver_sockaddr_init,
                        grpc_resolver_sockaddr_shutdown);
   grpc_register_plugin(grpc_load_reporting_plugin_init,
                        grpc_load_reporting_plugin_shutdown);
-  // The following lines are commented out in Chromium so that we don't
-  // introduce dependency on nanopb.
-  // grpc_register_plugin(grpc_lb_policy_grpclb_init,
-  //                      grpc_lb_policy_grpclb_shutdown);
   grpc_register_plugin(grpc_lb_policy_pick_first_init,
                        grpc_lb_policy_pick_first_shutdown);
   grpc_register_plugin(grpc_lb_policy_round_robin_init,
                        grpc_lb_policy_round_robin_shutdown);
-  // The following lines are commented out in Chromium so that we don't
-  // introduce dependency on nanopb.
-  // grpc_register_plugin(census_grpc_plugin_init,
-  //                      census_grpc_plugin_shutdown);
 }