Avoid allocating a whole new page for two one-element arrays when finalizing the VM isolate.

runtime/vm/pages.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_PAGES_H_
 #define RUNTIME_VM_PAGES_H_
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/lockers.h"
@@ skipping 302 matching lines @@
   uword TryAllocatePromoLocked(intptr_t size, GrowthPolicy growth_policy);
 
   // Bump block allocation from generated code.
   uword* TopAddress() { return &bump_top_; }
   uword* EndAddress() { return &bump_end_; }
   static intptr_t top_offset() { return OFFSET_OF(PageSpace, bump_top_); }
   static intptr_t end_offset() { return OFFSET_OF(PageSpace, bump_end_); }
 
   void SetupImagePage(void* pointer, uword size, bool is_executable);
 
+  // Return any bump allocation block to the freelist.
+  void AbandonBumpAllocation();
+
  private:
   // Ids for time and data records in Heap::GCStats.
   enum {
     // Time
     kConcurrentSweep = 0,
     kSafePoint = 1,
     kMarkObjects = 2,
     kResetFreeLists = 3,
     kSweepPages = 4,
     kSweepLargePages = 5,
@@ skipping 13 matching lines @@
                             bool is_locked);
   uword TryAllocateInFreshPage(intptr_t size,
                                HeapPage::PageType type,
                                GrowthPolicy growth_policy,
                                bool is_locked);
   uword TryAllocateDataBumpInternal(intptr_t size,
                                     GrowthPolicy growth_policy,
                                     bool is_locked);
   // Makes bump block walkable; do not call concurrently with mutator.
   void MakeIterable() const;
-  // Return any bump allocation block to the freelist.
-  void AbandonBumpAllocation();
   HeapPage* AllocatePage(HeapPage::PageType type);
   void FreePage(HeapPage* page, HeapPage* previous_page);
   HeapPage* AllocateLargePage(intptr_t size, HeapPage::PageType type);
   void TruncateLargePage(HeapPage* page, intptr_t new_object_size_in_bytes);
   void FreeLargePage(HeapPage* page, HeapPage* previous_page);
   void FreePages(HeapPage* pages);
   HeapPage* NextPageAnySize(HeapPage* page) const {
     ASSERT((pages_tail_ == NULL) || (pages_tail_->next() == NULL));
     ASSERT((exec_pages_tail_ == NULL) || (exec_pages_tail_->next() == NULL));
     if (page == pages_tail_) {
@@ skipping 59 matching lines @@
   friend class HeapIterationScope;
   friend class PageSpaceController;
   friend class SweeperTask;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_PAGES_H_