Remove hack around aborting loop body in the case of for loops and while loops.

sdk/lib/_internal/compiler/implementation/ssa/nodes.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
@@ skipping 202 matching lines @@
   }
 
   void assignDominators() {
     // Run through the blocks in order of increasing ids so we are
     // guaranteed that we have computed dominators for all blocks
     // higher up in the dominator tree.
     for (int i = 0, length = blocks.length; i < length; i++) {
       HBasicBlock block = blocks[i];
       List<HBasicBlock> predecessors = block.predecessors;
       if (block.isLoopHeader()) {
-        assert(predecessors.length >= 2);
         block.assignCommonDominator(predecessors[0]);
       } else {
         for (int j = predecessors.length - 1; j >= 0; j--) {
           block.assignCommonDominator(predecessors[j]);
         }
       }
     }
   }
 
   bool isValid() {
@@ skipping 2768 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty);
     return statements.last.end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }