DefNewGeneration::allocate and DefNewGeneration::par_allocate both have this code:

#if INCLUDE_ALL_GCS
 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
    if (_old_gen != NULL) {
       _old_gen->sample_eden_chunk();
     }
#endif

_old_gen is TenuredGeneration when running with Serial, which uses the default sample_eden_chunk() implementation in Generation:
  virtual void sample_eden_chunk() {}

_old_gen is ConcurrentMarkSweepGeneration when running with CMS, which uses:
  void sample_eden_chunk() {
    //Delegate to collector
    return collector()->sample_eden_chunk();
  }

and this is the code in CMSCollector's sample_eden_chunk:
void CMSCollector::sample_eden_chunk() {
  if (CMSEdenChunksRecordAlways && _eden_chunk_array != NULL) {

Note also that CMSEdenChunksRecordAlways is always true, even when we're not running with CMS.

I propose that we get rid of the CMSEdenChunksRecordAlways check in defNewGeneration.cpp.