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;
+
+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 dead after this
+  // operation, though we won't finalize them until the next GC discovers this.
+  // Useful for atomically applying behavior and schema changes.
+  static void ElementsForwardIdentity(const Array& before, const Array& after);
+
+  // For completeness, Smalltalk also has a two-way bulk become
+  // (Array>>#elementsExchangeIdentityWith:). This is typically used in
+  // application-level virtual memory or persistence schemes, where a set of
+  // objects are swapped with so-called husks and the original objects are
+  // serialized.
+  // static void ElementsExchangeIdentity(const Array& before,
+  //                                      const Array& after);
+};
+
+}  // namespace dart
+
+#endif  // VM_BECOME_H_