[cleanup] Fix conversion of string to array.

Also add a comment pointing to a more efficient alternative to
modular::to_array.

TEST=No functional change.

Change-Id: I073ca615d3abea4fc2273fe3263e262749531470
diff --git a/bin/ledger/testing/ledger_test_instance_provider/ledger_test_instance_provider.cc b/bin/ledger/testing/ledger_test_instance_provider/ledger_test_instance_provider.cc
index b7158e8..7366005 100644
--- a/bin/ledger/testing/ledger_test_instance_provider/ledger_test_instance_provider.cc
+++ b/bin/ledger/testing/ledger_test_instance_provider/ledger_test_instance_provider.cc
@@ -54,9 +54,8 @@
   // Serve the repository.
   context->outgoing().AddPublicService<fuchsia::ledger::Ledger>(
       [&repository](fidl::InterfaceRequest<fuchsia::ledger::Ledger> request) {
-        repository->GetLedger(
-            convert::ExtendedStringView(kLedgerName).ToArray(),
-            std::move(request));
+        repository->GetLedger(convert::ToArray(kLedgerName),
+                              std::move(request));
       });
   loop.Run();
   return EXIT_SUCCESS;
diff --git a/lib/fidl/array_to_string.h b/lib/fidl/array_to_string.h
index 2f9c0f6..fa8467a 100644
--- a/lib/fidl/array_to_string.h
+++ b/lib/fidl/array_to_string.h
@@ -51,6 +51,7 @@
   return to_hex_string(data.data(), data.size());
 }
 
+// If possible use convert::ToArray instead.
 inline fidl::VectorPtr<uint8_t> to_array(const std::string& val) {
   fidl::VectorPtr<uint8_t> ret = fidl::VectorPtr<uint8_t>::New(0);
   for (char c : val) {