If a large object is truncated, also truncate the page.

runtime/vm/virtual_memory.h

 // Copyright (c) 2012, 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 VM_VIRTUAL_MEMORY_H_
 #define VM_VIRTUAL_MEMORY_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/memory_region.h"
@@ skipping 44 matching lines @@
   static VirtualMemory* ReserveAligned(intptr_t size, intptr_t alignment);
 
   static intptr_t PageSize() {
     ASSERT(page_size_ != 0);
     ASSERT(Utils::IsPowerOfTwo(page_size_));
     return page_size_;
   }
 
   static bool InSamePage(uword address0, uword address1);
 
- private:
   // Truncate this virtual memory segment.
   void Truncate(uword new_start, intptr_t size);
 
+ private:
   // Free a sub segment. On operating systems that support it this
   // can give back the virtual memory to the system.
   void FreeSubSegment(void* address, intptr_t size);
 
   // This constructor is only used internally when reserving new virtual spaces.
   // It does not reserve any virtual address space on its own.
   VirtualMemory(const MemoryRegion& region, void* reserved_pointer) :
       region_(region.pointer(), region.size()),
       reserved_pointer_(reserved_pointer) { }
 
@@ skipping 11 matching lines @@
   void* reserved_pointer_;
 
   static uword page_size_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 
 }  // namespace dart
 
 #endif  // VM_VIRTUAL_MEMORY_H_