G1: Use SoftMaxHeapSize to guide GC heuristics

*** 69,97 ****
    bool _clearing_next_bitmap;
  
    // Set during a full gc pause.
    bool _in_full_gc;
  
  public:
    G1CollectorState() :
      _in_young_only_phase(true),
      _in_young_gc_before_mixed(false),
  
      _in_initial_mark_gc(false),
      _initiate_conc_mark_if_possible(false),
  
      _mark_or_rebuild_in_progress(false),
      _clearing_next_bitmap(false),
!     _in_full_gc(false) { }
  
    // Phase setters
    void set_in_young_only_phase(bool v) { _in_young_only_phase = v; }
  
    // Pause setters
    void set_in_young_gc_before_mixed(bool v) { _in_young_gc_before_mixed = v; }
    void set_in_initial_mark_gc(bool v) { _in_initial_mark_gc = v; }
    void set_in_full_gc(bool v) { _in_full_gc = v; }
  
    void set_initiate_conc_mark_if_possible(bool v) { _initiate_conc_mark_if_possible = v; }
  
    void set_mark_or_rebuild_in_progress(bool v) { _mark_or_rebuild_in_progress = v; }
    void set_clearing_next_bitmap(bool v) { _clearing_next_bitmap = v; }
--- 69,102 ----
    bool _clearing_next_bitmap;
  
    // Set during a full gc pause.
    bool _in_full_gc;
  
+   // Indicate finish of mixed gc(s)
+   bool _finish_of_mixed_gc;
+ 
  public:
    G1CollectorState() :
      _in_young_only_phase(true),
      _in_young_gc_before_mixed(false),
  
      _in_initial_mark_gc(false),
      _initiate_conc_mark_if_possible(false),
  
      _mark_or_rebuild_in_progress(false),
      _clearing_next_bitmap(false),
!     _in_full_gc(false),
!     _finish_of_mixed_gc(false) { }
  
    // Phase setters
    void set_in_young_only_phase(bool v) { _in_young_only_phase = v; }
  
    // Pause setters
    void set_in_young_gc_before_mixed(bool v) { _in_young_gc_before_mixed = v; }
    void set_in_initial_mark_gc(bool v) { _in_initial_mark_gc = v; }
    void set_in_full_gc(bool v) { _in_full_gc = v; }
+   void set_finish_of_mixed_gc(bool v) { _finish_of_mixed_gc = v; }
  
    void set_initiate_conc_mark_if_possible(bool v) { _initiate_conc_mark_if_possible = v; }
  
    void set_mark_or_rebuild_in_progress(bool v) { _mark_or_rebuild_in_progress = v; }
    void set_clearing_next_bitmap(bool v) { _clearing_next_bitmap = v; }
*** 107,116 ****
--- 112,122 ----
  
    bool initiate_conc_mark_if_possible() const { return _initiate_conc_mark_if_possible; }
  
    bool mark_or_rebuild_in_progress() const { return _mark_or_rebuild_in_progress; }
    bool clearing_next_bitmap() const { return _clearing_next_bitmap; }
+   bool finish_of_mixed_gc() const { return _finish_of_mixed_gc; }
  
    G1YCType yc_type() const {
      if (in_initial_mark_gc()) {
        return InitialMark;
      } else if (mark_or_rebuild_in_progress()) {