At SSA build-time, change the block information that we attach to loop with aborting bodies.

sdk/lib/_internal/compiler/implementation/ssa/codegen.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;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 813 matching lines @@
       currentBlockInformation = info.body.start.blockFlow.body;
       generateStatements(info.body);
       currentBlockInformation = oldInfo;
     } else {
       generateStatements(info.body);
     }
   }
 
   bool visitLoopInfo(HLoopBlockInformation info) {
     HExpressionInformation condition = info.condition;
-    bool isConditionExpression = condition == null || isJSCondition(condition);
+    bool isConditionExpression = isJSCondition(condition);
 
     js.Loop loop;
 
     switch (info.kind) {
       // Treate all three "test-first" loops the same way.
       case HLoopBlockInformation.FOR_LOOP:
       case HLoopBlockInformation.WHILE_LOOP:
       case HLoopBlockInformation.FOR_IN_LOOP:
         HBlockInformation initialization = info.initializer;
         int initializationType = TYPE_STATEMENT;
@@ skipping 110 matching lines @@
         js.Statement body = new js.Block.empty();
         currentContainer = body;
         if (!isConditionExpression || info.updates != null) {
           wrapLoopBodyForContinue(info);
         } else {
           visitBodyIgnoreLabels(info);
         }
         if (info.updates != null) {
           generateStatements(info.updates);
         }
-        if (condition == null) {
-          push(newLiteralBool(false));
-        } else if (isConditionExpression) {
+        if (isConditionExpression) {
           push(generateExpression(condition));
         } else {
           generateStatements(condition);
           use(condition.conditionExpression);
         }
         js.Expression jsCondition = pop();
         currentContainer = oldContainer;
         body = unwrapStatement(body);
         loop = new js.Do(body, jsCondition);
         break;
@@ skipping 2125 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }