Fuchsia: Memory reservation and partial unmapping

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 RUNTIME_VM_VIRTUAL_MEMORY_H_
 #define RUNTIME_VM_VIRTUAL_MEMORY_H_
 
 #include "platform/utils.h"
 #include "vm/globals.h"
 #include "vm/memory_region.h"
@@ skipping 55 matching lines @@
 
   bool embedder_allocated() const { return embedder_allocated_; }
 
   static VirtualMemory* ForExternalPage(void* pointer, uword size);
 
  private:
   static VirtualMemory* ReserveInternal(intptr_t size);
 
   // Free a sub segment. On operating systems that support it this
   // can give back the virtual memory to the system. Returns true on success.
-  static bool FreeSubSegment(void* address, intptr_t size);
+  static bool FreeSubSegment(int32_t handle, 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.
   explicit VirtualMemory(const MemoryRegion& region, int32_t handle = 0)
       : region_(region.pointer(), region.size()),
         reserved_size_(region.size()),
         handle_(handle),
         embedder_allocated_(false) {}
 
   MemoryRegion region_;
 
   // The size of the underlying reservation not yet given back to the OS.
   // Its start coincides with region_, but its size might not, due to Truncate.
   intptr_t reserved_size_;
 
   int32_t handle_;
 
   static uword page_size_;
 
   // True for a region provided by the embedder.
   bool embedder_allocated_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_VIRTUAL_MEMORY_H_