Added max length comments for some lb proto fields

src/proto/grpc/lb/v1/load_balancer.proto

@@ -63,7 +63,8 @@ message LoadBalanceRequest {
 }
 
 message InitialLoadBalanceRequest {
-  // Name of load balanced service (IE, service.grpc.gslb.google.com)
+  // Name of load balanced service (IE, service.grpc.gslb.google.com). Its
+  // length should be less than 128 bytes.
   string name = 1;
 }
 
@@ -95,7 +96,8 @@ message InitialLoadBalanceResponse {
   // This is an application layer redirect that indicates the client should use
   // the specified server for load balancing. When this field is non-empty in
   // the response, the client should open a separate connection to the
-  // load_balancer_delegate and call the BalanceLoad method.
+  // load_balancer_delegate and call the BalanceLoad method. Its length should
+  // be less than 64 bytes.
   string load_balancer_delegate = 1;
 
   // This interval defines how often the client should send the client stats