Replaced different means of zone pooling/reusing by one zone segment pool

src/zone/zone.h

Index: src/zone/zone.h
diff --git a/src/zone/zone.h b/src/zone/zone.h
index ad64af27f699d62eea0a1b0ce7123fe92fb6af2e..40fd1a82c30c98a425552580fc949062686832f5 100644
--- a/src/zone/zone.h
+++ b/src/zone/zone.h
@@ -44,14 +44,6 @@ class Zone final {
     return static_cast<T*>(New(length * sizeof(T)));
   }
 
-  // Deletes all objects and free all memory allocated in the Zone. Keeps one
-  // small (size <= kMaximumKeptSegmentSize) segment around if it finds one.
-  void DeleteAll();
-
-  // Deletes the last small segment kept around by DeleteAll(). You
-  // may no longer allocate in the Zone after a call to this method.
-  void DeleteKeptSegment();
-
   // Returns true if more memory has been allocated in zones than
   // the limit allows.
   bool excess_allocation() const {
@@ -62,6 +54,9 @@ class Zone final {
 
   AccountingAllocator* allocator() const { return allocator_; }
 
+  // Deletes all objects and free all memory allocated in the Zone.
+  void DeleteAll();
+
  private:
 // All pointers returned from New() have this alignment.  In addition, if the
 // object being allocated has a size that is divisible by 8 then its alignment
@@ -79,9 +74,6 @@ class Zone final {
   // Never allocate segments larger than this size in bytes.
   static const size_t kMaximumSegmentSize = 1 * MB;
 
-  // Never keep segments larger than this size in bytes around.
-  static const size_t kMaximumKeptSegmentSize = 64 * KB;
-
   // Report zone excess when allocation exceeds this limit.
   static const size_t kExcessLimit = 256 * MB;
 
@@ -133,19 +125,6 @@ class ZoneObject {
   void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); }
 };
 
-// The ZoneScope is used to automatically call DeleteAll() on a
-// Zone when the ZoneScope is destroyed (i.e. goes out of scope)
-class ZoneScope final {
- public:
-  explicit ZoneScope(Zone* zone) : zone_(zone) {}
-  ~ZoneScope() { zone_->DeleteAll(); }
-
-  Zone* zone() const { return zone_; }
-
- private:
-  Zone* zone_;
-};
-
 // The ZoneAllocationPolicy is used to specialize generic data
 // structures to allocate themselves and their elements in the Zone.
 class ZoneAllocationPolicy final {