dart2js: Fix SSA corner case with always breaking loop and failing assert

tests/language/unconditional_break.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Test to ensure that we get don't exceptions in the SSA verifier when

[ngeoffray, 2013/04/07 09:48:50]

get don't -> don't get

+// generating phi for the return value of an inlined function that contains a
+// loop that always breaks.
+doWhileBreak() {
+  do {
+    break;
+  } while (true);
+}
+
+main() {
+  doWhileBreak();
+}