Fix incorrect MIME type for .js files loaded through CordovaResourceAPI.

This fixes devtools complaining about .js files being served as "text/plain"
when they have gone through remapUrl().

framework/src/org/apache/cordova/CordovaResourceApi.java

@@ -188,6 +188,9 @@ public class CordovaResourceApi {
         extension = extension.toLowerCase(Locale.getDefault());
         if (extension.equals("3ga")) {
             return "audio/3gpp";
+        } else if (extension.equals("js")) {
+            // Missing from the map :(.
+            return "text/javascript";
         }
         return MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
     }