Cland tidy fixes for channelz

src/core/ext/filters/client_channel/client_channel_channelz.cc

@@ -69,7 +69,7 @@ void ClientChannelNode::PopulateChildRefs(grpc_json* json) {
   grpc_json* json_iterator = nullptr;
   grpc_client_channel_populate_child_refs(client_channel_, &child_subchannels,
                                           &child_channels);
-  if (child_subchannels.size() > 0) {
+  if (!child_subchannels.empty()) {
     grpc_json* array_parent = grpc_json_create_child(
         nullptr, json, "subchannelRef", nullptr, GRPC_JSON_ARRAY, false);
     for (size_t i = 0; i < child_subchannels.size(); ++i) {
@@ -80,7 +80,7 @@ void ClientChannelNode::PopulateChildRefs(grpc_json* json) {
                                         child_subchannels[i]);
     }
   }
-  if (child_channels.size() > 0) {
+  if (!child_channels.empty()) {
     grpc_json* array_parent = grpc_json_create_child(
         nullptr, json, "channelRef", nullptr, GRPC_JSON_ARRAY, false);
     json_iterator = nullptr;

src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc

@@ -59,7 +59,7 @@ class PickFirst : public LoadBalancingPolicy {
   void PingOneLocked(grpc_closure* on_initiate, grpc_closure* on_ack) override;
   void ExitIdleLocked() override;
   void FillChildRefsForChannelz(ChildRefsList* child_subchannels,
-                                ChildRefsList* child_channels) override;
+                                ChildRefsList* ignored) override;
 
  private:
   ~PickFirst();
@@ -181,7 +181,7 @@ void PickFirst::HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) {
 }
 
 void PickFirst::ShutdownLocked() {
-  AutoChildRefsUpdater(this);
+  AutoChildRefsUpdater gaurd(this);
   grpc_error* error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Channel shutdown");
   if (grpc_lb_pick_first_trace.enabled()) {
     gpr_log(GPR_INFO, "Pick First %p Shutting down", this);

src/core/ext/filters/client_channel/subchannel.cc

@@ -390,8 +390,8 @@ grpc_subchannel* grpc_subchannel_create(grpc_connector* connector,
 }
 
 grpc_core::channelz::SubchannelNode* grpc_subchannel_get_channelz_node(
-    grpc_subchannel* s) {
-  return s->channelz_subchannel.get();
+    grpc_subchannel* subchannel) {
+  return subchannel->channelz_subchannel.get();
 }
 
 static void continue_connect_locked(grpc_subchannel* c) {