[deoptimizer] Preserve double bit patterns correctly.

test/mjsunit/regress/regress-crbug-684208.js

Index: test/mjsunit/regress/regress-crbug-684208.js
diff --git a/test/mjsunit/regress/regress-crbug-684208.js b/test/mjsunit/regress/regress-crbug-684208.js
new file mode 100644
index 0000000000000000000000000000000000000000..7055a7eb821a50b4bd983684e220daadd150fb56
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-684208.js
@@ -0,0 +1,15 @@
+// Copyright 2017 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
+
+function foo() {
+  var a = [1, 2.3, /*hole*/, 4.2];
+  %_DeoptimizeNow();
+  return a[2];
+}
+assertSame(undefined, foo());
+assertSame(undefined, foo());
+%OptimizeFunctionOnNextCall(foo)
+assertSame(undefined, foo());