How to use the feature of “Default variable”

[Fu, Junwei]

Hi All,

I want to use the feature of “Default variable” that descripted in 
https://issues.apache.org/jira/browse/CB-9162.
Is it means that the line of  <preference value="ENABLE_LOG" value="true" /> 
will be added automatically in config.xml if specified <preference 
value="ENABLE_LOG" default="true" /> in the plugin.xml,

But   there is no default ENABLE_LOG in config.xml but in 
cordova/plugins/android.json when I config  when I installed the  
org.test.defaultvariables plugin.

Thanks,
Junwei.