[crankshaft] Fix crash when case labels inline endless loops

test/mjsunit/regress/regress-crbug-551287.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.
 
 // Flags: --allow-natives-syntax
 
-function foo(x) {
-  if (x === undefined) return;
-  while (true) {
-    while (1 || 2) { }
-    f();
+function f() { do { } while (true); }
+
+function boom(x) {
+  switch(x) {
+    case 1:
+    case f(): return;
   }
 }
-%OptimizeFunctionOnNextCall(foo);
-foo();
+
+%OptimizeFunctionOnNextCall(boom)
+boom(1);