Initial isolate reload support

runtime/vm/become.h

Index: runtime/vm/become.h
diff --git a/runtime/vm/become.h b/runtime/vm/become.h
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+// Copyright (c) 2016, 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_BECOME_H_
+#define VM_BECOME_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+class Array;
+
+// TODO(johnmccutchan): Refactor this class so that it is not all static and
+// provides utility methods for building the mapping of before and after.
+class Become : public AllStatic {
+ public:
+  // Smalltalk's one-way bulk become (Array>>#elementsForwardIdentityTo:).
+  // Redirects all pointers to elements of 'before' to the corresponding element
+  // in 'after'. Every element in 'before' is guaranteed to be not reachable.
+  // Useful for atomically applying behavior and schema changes.
+  static void ElementsForwardIdentity(const Array& before, const Array& after);
+};
+
+}  // namespace dart
+
+#endif  // VM_BECOME_H_