Remove FLAG_min_preparse_length.

test/mjsunit/bugs/bug-2728.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.
+
+// from test/webkit/fast/js/kde/parse.js
+assertThrows("function test() { while(0) break lab; } lab: 1");
+assertThrows("function test() { while(0) continue lab; } lab: 1");
+assertThrows("function test() { while(0) break lab } lab: 1");
+assertThrows("function test() { while(0) continue lab } lab: 1");
+
+// from test/webkit/fast/js/parser-syntax-check.js
+assertThrows("break ; break your_limits ; continue ; continue living ; debugger");
+assertThrows("function f() { break ; break your_limits ; continue ; continue living ; debugger }");
+assertThrows("try { break } catch(e) {}");
+assertThrows("function f() { try { break } catch(e) {} }");
+assertThrows("L: L: ;");
+assertThrows("function f() { L: L: ; }");
+assertThrows("L: L1: L: ;");
+assertThrows("function f() { L: L1: L: ; }");
+assertThrows("L: L1: L2: L3: L4: L: ;");
+assertThrows("function f() { L: L1: L2: L3: L4: L: ; }");