Introduce simple Thread class to support gradual refactoring of interfaces.

runtime/vm/allocation.h

 // Copyright (c) 2013, 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_ALLOCATION_H_
 #define VM_ALLOCATION_H_
 
 #include "platform/assert.h"
 #include "vm/base_isolate.h"
 #include "vm/globals.h"
@@ skipping 75 matching lines @@
 // Zone allocated objects cannot be individually deallocated, but have
 // to rely on the destructor of Zone which is called when the Zone
 // goes out of scope to reclaim memory.
 class ZoneAllocated {
  public:
   ZoneAllocated() { }
 
   // Implicitly allocate the object in the current zone.
   void* operator new(uword size);
 
+  // DEPRECATED: Use Zone version.
   // Implicitly allocate the object in the current zone given the current
   // isolate.
   void* operator new(uword size, BaseIsolate* isolate);
 
   // Allocate the object in the given zone, which must be the current zone.
   void* operator new(uword size, Zone* zone);
 
   // Ideally, the delete operator should be protected instead of
   // public, but unfortunately the compiler sometimes synthesizes
   // (unused) destructors for classes derived from ZoneObject, which
   // require the operator to be visible. MSVC requires the delete
   // operator to be public.
 
   // Disallow explicit deallocation of nodes. Nodes can only be
   // deallocated by invoking DeleteAll() on the zone they live in.
   void operator delete(void* pointer) { UNREACHABLE(); }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ZoneAllocated);
 };
 
 }  // namespace dart
 
 #endif  // VM_ALLOCATION_H_