[turbofan] Handle cyclic dependencies in context typing.

test/mjsunit/compiler/regress-451012.js

Index: test/mjsunit/compiler/regress-451012.js
diff --git a/test/mjsunit/regress/regress-crbug-450642.js b/test/mjsunit/compiler/regress-451012.js
similarity index 69%
copy from test/mjsunit/regress/regress-crbug-450642.js
copy to test/mjsunit/compiler/regress-451012.js
index 7f821e0ffc0cba83ca4544d9b61041e49d97d90e..bffc8bc5bdfac32bb561a24153d00157b26ac3a5 100644
--- a/test/mjsunit/regress/regress-crbug-450642.js
+++ b/test/mjsunit/compiler/regress-451012.js
@@ -2,4 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-assertThrows(function() { with (undefined) {} }, TypeError);
+"use strict";
+function f() {
+  for (let v; v; ) {
+    let x;
+  }
+}
+
+f();