Make unused semispace available to other isolates.

runtime/vm/memory_region.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_MEMORY_REGION_H_
 #define VM_MEMORY_REGION_H_
 
 #include "platform/assert.h"
+#include "vm/allocation.h"
 #include "vm/globals.h"
 
 namespace dart {
 
 // Memory regions are useful for accessing memory with bounds check in
 // debug mode. They can be safely passed by value and do not assume ownership
 // of the region.
-class MemoryRegion {
+class MemoryRegion : public ValueObject {
  public:
   MemoryRegion() : pointer_(NULL), size_(0) { }
   MemoryRegion(void* pointer, uword size) : pointer_(pointer), size_(size) { }
+  MemoryRegion(const MemoryRegion& other) : ValueObject() { *this = other; }
+  MemoryRegion& operator=(const MemoryRegion& other) {
+    pointer_ = other.pointer_;
+    size_ = other.size_;
+    return *this;
+  }
 
   void* pointer() const { return pointer_; }
   uword size() const { return size_; }
   uword size_in_bits() const { return size_ * kBitsPerByte; }
 
   static uword pointer_offset() { return OFFSET_OF(MemoryRegion, pointer_); }
 
   uword start() const { return reinterpret_cast<uword>(pointer_); }
   uword end() const { return start() + size_; }
 
@@ skipping 31 matching lines @@
 
  private:
   template<typename T> T* ComputeInternalPointer(uword offset) const {
     ASSERT(size() >= sizeof(T));
     ASSERT(offset <= size() - sizeof(T));
     return reinterpret_cast<T*>(start() + offset);
   }
 
   void* pointer_;
   uword size_;
-
-  DISALLOW_COPY_AND_ASSIGN(MemoryRegion);
 };
 
 }  // namespace dart
 
 #endif  // VM_MEMORY_REGION_H_