Pool implementation for zone segments

src/zone/zone.h

Index: src/zone/zone.h
diff --git a/src/zone/zone.h b/src/zone/zone.h
index 0bf7f28a8442f87823f10a96363360d7d933d54d..eeea358239a2f8609748f4c9fa0ffa7f2aaff13c 100644
--- a/src/zone/zone.h
+++ b/src/zone/zone.h
@@ -25,7 +25,7 @@ namespace internal {
 //
 // Note: There is no need to initialize the Zone; the first time an
 // allocation is attempted, a segment of memory will be requested
-// through a call to malloc().
+// through the allocator.
 //
 // Note: The implementation is inherently not thread safe. Do not use
 // from multi-threaded code.
@@ -44,14 +44,9 @@ class V8_EXPORT_PRIVATE 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.
+  // Deletes all objects and free all memory allocated in the Zone.
   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 {
@@ -80,9 +75,6 @@ class V8_EXPORT_PRIVATE 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;
 
@@ -102,7 +94,7 @@ class V8_EXPORT_PRIVATE Zone final {
 
   // Creates a new segment, sets it size, and pushes it to the front
   // of the segment chain. Returns the new segment.
-  inline Segment* NewSegment(size_t size);
+  inline Segment* NewSegment(size_t requested_size);
 
   // The free region in the current (front) segment is represented as
   // the half-open interval [position, limit). The 'position' variable