[turbofan] Reducers should revisit end after merging to it.

test/mjsunit/compiler/regress-dead-throw-inlining.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
 
-Array.prototype.__proto__ = null;
-var prototype = Array.prototype;
-function f() {
-  prototype.lastIndexOf({});
-}
+function g() { if (false) throw 0; }
+function f() { g(); }
+
 f();
 f();
 %OptimizeFunctionOnNextCall(f);
 f();