Simplify and fix the rewriter

test/mjsunit/es6/completion.js

 // Copyright 2015 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.
 
 
 function assertUndef(x) {
   assertEquals(undefined, x);
 }
 
 
@@ skipping 128 matching lines @@
 assertUndef(eval("var x = 1;"));
 assertEquals(1, eval("if (true) { 1; } else { 2; }"));
 assertEquals(2, eval("if (false) { 1; } else { 2; }"));
 assertUndef(eval("try{1; if (true) { 2; throw ''; } else { 2; }} catch(e){}"));
 assertEquals(2, eval("1; var i = 0; do { ++i; 2; } while(i!=1);"));
 assertUndef(eval(
     "try{1; var i = 0; do { ++i; 2; throw ''; } while (i!=1);} catch(e){}"));
 assertUndef(eval("1; try{2; throwOnReturn();} catch(e){}"));
 assertUndef(eval("1; twoFunc();"));
 assertEquals(2, eval("1; with ( { a: 0 } ) { 2; }"));
+
+assertUndef(eval('a: while(true) { do { 0 } while(false); switch(1) { case 0: 1; case 1: break a; }; 0 }'));
+assertUndef(eval('a: while(true) { do { 0 } while(false); try {} finally { break a }; 0 }'));
+assertUndef(eval('a: while(true) { b: while(true) { 0; break b; }; switch(1) { case 1: break a; }; 2 }'));
+assertUndef(eval('a: while(true) { b: while(true) { 0; break b; }; while (true) { break a; }; 2 }'));
+assertUndef(eval('while (true) { 20; a:{ break a; }  with ({}) break; 30; }'));
+assertEquals(42, eval('a: while(true) { switch(0) { case 0: 42; case 1: break a; }; 33 }'));