Measures aggregated by the platform (for instance test_success_density or coverage) should not be send by language plugin.
The list of allowed metrics that can be send in the report are available here : https://github.com/SonarSource/sonarqube/blob/master/sonar-core/src/main/java/org/sonar/core/metric/BatchMetrics.java
If the plugin try to such such measures, they are ignored and a log message is displayed in the server console (at DEBUG level). For instance :
2015.07.27 17:17:41 DEBUG web[o.s.s.c.m.ReportMetricValidatorImpl] The metric 'test_success_density' is ignored and should not be send in the batch report