message: Make LoadBufferFromGCS virtual.
diff: @@ -261,7 +261,7 @@ class GcsFileSystem : public FileSystem {
  size_t block_size, size_t max_bytes, uint64 max_staleness);
  /// Loads file contents from GCS for a given filename, offset, and length.
  - Status LoadBufferFromGCS(const string& fname, size_t offset, size_t n,
  + virtual Status LoadBufferFromGCS(const string& fname, size_t offset, size_t n,
  char* buffer, size_t* bytes_transferred);
  std::shared_ptr<ComputeEngineMetadataClient> compute_engine_metadata_client_;
  