code: public void setEnabled(boolean enabled) {
          setEnabled(enabled, ENABLED_MASK);
          if (enabled) {
              Log parent;
              if ((parent = mParent) != null) {
                  parent.setEnabled(true);
              }
          }
      }
docs: When this Log is enabled, all parent Logs are also enabled. When this
  Log is disabled, parent Logs are unaffected.