[regexp] clear QuickCheckDetails for backward reads.

test/mjsunit/regress/regress-crbug-570241.js

Index: test/mjsunit/regress/regress-crbug-570241.js
diff --git a/test/mjsunit/regress/regress-crbug-570241.js b/test/mjsunit/regress/regress-crbug-570241.js
new file mode 100644
index 0000000000000000000000000000000000000000..4fecba57b5a96c77852e9b0b97ff8d2228957e01
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+++ b/test/mjsunit/regress/regress-crbug-570241.js
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+// Copyright 2013 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: --harmony-regexp-lookbehind
+
+assertTrue(/(?<=12345123451234512345)/.test("12345123451234512345"));