Fix grpclb LB policy pick method to return 0 upon error.
diff --git a/src/core/ext/client_config/lb_policy.h b/src/core/ext/client_config/lb_policy.h
index 6cc3e1e..110d08f 100644
--- a/src/core/ext/client_config/lb_policy.h
+++ b/src/core/ext/client_config/lb_policy.h
@@ -142,15 +142,18 @@
void grpc_lb_policy_init(grpc_lb_policy *policy,
const grpc_lb_policy_vtable *vtable);
-/** Find an appropriate target for this call, based on \a pick_args.
- Picking can be synchronous or asynchronous. In the synchronous case, when a
- pick is readily available, it'll be returned in \a target and a non-zero
- value will be returned.
- In the asynchronous case, zero is returned and \a on_complete will be called
- once \a target and \a user_data have been set. Any IO should be done under
- \a pick_args->pollent. The opaque \a user_data output argument corresponds
- to information that may need be propagated from the LB policy. It may be
- NULL. Errors are signaled by receiving a NULL \a *target. */
+/** Finds an appropriate subchannel for a call, based on \a pick_args.
+
+ \a target will be set to the selected subchannel, or NULL on failure.
+ Upon success, \a user_data will be set to whatever opaque information
+ may need to be propagated from the LB policy, or NULL if not needed.
+
+ If the pick succeeds and a result is known immediately, a non-zero
+ value will be returned. Otherwise, \a on_complete will be invoked
+ once the pick is complete with its error argument set to indicate
+ success or failure.
+
+ Any I/O should be done under \a pick_args->pollent. */
int grpc_lb_policy_pick(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
const grpc_lb_policy_pick_args *pick_args,
grpc_connected_subchannel **target, void **user_data,