Add const to DataLoader::IsBuildResponseReady()

#codehealth

PiperOrigin-RevId: 620827132

Author: hiroyuki-komatsu

src/engine/data_loader.cc

@@ -225,7 +225,7 @@ void DataLoader::MaybeBuildNewData() {
   }
 }
 
-bool DataLoader::IsBuildResponseReady() {
+bool DataLoader::IsBuildResponseReady() const {
   return loader_response_future_ && loader_response_future_->Ready();
 }
 

src/engine/data_loader.h

@@ -96,7 +96,7 @@ class DataLoader {
   void MaybeBuildNewData();
 
   // Returns true if a new data loader response is ready.
-  bool IsBuildResponseReady();
+  bool IsBuildResponseReady() const;
 
   // Maybe move the data loader response to the caller.
   // Otherwise nullptr is returned.