[turbofan] Fix typing rule for CheckBounds.

test/mjsunit/regress/regress-crbug-708050-1.js

Index: test/mjsunit/regress/regress-crbug-708050-1.js
diff --git a/test/mjsunit/regress/regress-crbug-708050-1.js b/test/mjsunit/regress/regress-crbug-708050-1.js
new file mode 100644
index 0000000000000000000000000000000000000000..be26e10c84920f6d9a3bd9cc3d90e778e22f789f
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-708050-1.js
@@ -0,0 +1,17 @@
+// 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
+
+var v = {}
+
+function foo() {
+  v[0] = 5;
+  v[-0] = 27;
+  return v[0];
+}
+
+assertEquals(27, foo());
+%OptimizeFunctionOnNextCall(foo);
+assertEquals(27, foo());