G1Analytics uses uninitialized fields

Both _recent_avg_pause_time_ratio and _last_pause_time_ratio are missing from the initialization list, and in effect will leave these fields uninitialized.

The following is a potential use before initialization situation:
---
        {
          size_t expand_bytes = _heap_sizing_policy->expansion_amount(); // USED HERE
          if (expand_bytes > 0) {
            size_t bytes_before = capacity();
            // No need for an ergo logging here,
            // expansion_amount() does this when it returns a value > 0.
            double expand_ms;
            if (!expand(expand_bytes, _workers, &expand_ms)) {
              // We failed to expand the heap. Cannot do anything about it.
            }
            g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
          }
        }

        // We redo the verification but now wrt to the new CSet which
        // has just got initialized after the previous CSet was freed.
        _cm->verify_no_cset_oops();

        // This timing is only used by the ergonomics to handle our pause target.
        // It is unclear why this should not include the full pause. We will
        // investigate this in CR 7178365.
        double sample_end_time_sec = os::elapsedTime();
        double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
        size_t total_cards_scanned = per_thread_states.total_cards_scanned();
        g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc); // SET HERE

---
do_collection_pause_at_safepoint
  record_collection_pause_end
    compute_pause_time_ratio
      sets _recent_avg_pause_time_ratio

---
do_collection_pause_at_safepoint
  expansion_amount
    reads _recent_avg_pause_time_ratio
    _recent_avg_pause_time_ratio(),
    _last_pause_time_ratio()