Fix double canonicalization

test/mjsunit/regress/regress-double-canonicalization.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+var ab = new ArrayBuffer(8);
+var i_view = new Int32Array(ab);
+i_view[0] = %GetHoleNaNUpper()
+i_view[1] = %GetHoleNaNLower();
+var hole_nan = (new Float64Array(ab))[0];
+
+var array = [];
+
+function write() {
+  array[0] = hole_nan;
+}
+
+write();
+%OptimizeFunctionOnNextCall(write);
+write();
+array[1] = undefined;
+assertTrue(isNaN(array[0]));
+assertEquals("number", typeof array[0]);