Improve performance when setting RC defaults (#469)

* Improve performance when setting RC defaults

* Update remote_config.i

Author: a-maurice

docs/readme.md

@@ -159,6 +159,8 @@ Release Notes
 - Changes
     - Auth (Android/iOS): Deprecate `PhoneAuthProvider.MaxTimeoutMs`. The actual
       range is determined by the underlying SDK, ex. [PhoneAuthOptions.Builder in Android SDK](https://firebase.google.com/docs/reference/android/com/google/firebase/auth/PhoneAuthOptions.Builder).
+    - Remote Config: Improve performance when setting default parameters
+      with long strings.
 
 ### 9.6.0
 - Changes

remote_config/src/swig/remote_config.i

@@ -198,26 +198,27 @@ struct ConfigValueInternal {
 
     foreach (System.Collections.Generic.KeyValuePair<string, object>
              pair in oldMap) {
-      string toStore;
-      if (pair.Value is System.Collections.Generic.IEnumerable<byte>) {
+      if (pair.Value is string) {
+        newMap[pair.Key] = pair.Value as string;
+      } else if (pair.Value is System.Collections.Generic.IEnumerable<byte>) {
         // For lists of bytes, match the UTF8 conversion used by the base
         // implementation.
         var list =
             new System.Collections.Generic.List<byte>(
                 pair.Value as System.Collections.Generic.IEnumerable<byte>);
-        toStore = System.Text.Encoding.UTF8.GetString(list.ToArray());
+        newMap[pair.Key] = System.Text.Encoding.UTF8.GetString(list.ToArray());
       } else if (pair.Value is System.Collections.IEnumerable) {
         // For other collections, just try to convert the inner values.
         var list = pair.Value as System.Collections.IEnumerable;
-        toStore = "";
+        var stringBuilder = new System.Text.StringBuilder();
         foreach (object obj in list) {
-          toStore += obj.ToString();
+          stringBuilder.Append(obj);
         }
+        newMap[pair.Key] = stringBuilder.ToString();
       } else {
         // For everything else, go straight to a string.
-        toStore = pair.Value.ToString();
+        newMap[pair.Key] = pair.Value.ToString();
       }
-      newMap[pair.Key] = toStore;
     }
 
     return newMap;