Add ChannelArguments::SetLoadBalancingPolicyName() to C++ API.

include/grpc++/support/channel_arguments.h

@@ -80,6 +80,11 @@ class ChannelArguments {
   /// The given string will be sent at the front of the user agent string.
   void SetUserAgentPrefix(const grpc::string& user_agent_prefix);
 
+  // Set LB policy name.
+  // Note that if the name resolver returns only balancer addresses, the
+  // grpclb LB policy will be used, regardless of what is specified here.
+  void SetLoadBalancingPolicyName(const grpc::string& lb_policy_name);
+
   // Generic channel argument setters. Only for advanced use cases.
   /// Set an integer argument \a value under \a key.
   void SetInt(const grpc::string& key, int value);

src/cpp/common/channel_arguments.cc

@@ -113,6 +113,11 @@ void ChannelArguments::SetUserAgentPrefix(
   }
 }
 
+void ChannelArguments::SetLoadBalancingPolicyName(
+    const grpc::string& lb_policy_name) {
+  SetString(GRPC_ARG_LB_POLICY_NAME, lb_policy_name);
+}
+
 void ChannelArguments::SetInt(const grpc::string& key, int value) {
   grpc_arg arg;
   arg.type = GRPC_ARG_INTEGER;