dart2js: Bugfix for when 'await' occurs in an initializer list.

pkg/compiler/lib/src/js/rewrite_async.dart

 // Copyright (c) 2015, 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.
 
 library rewrite_async;
 
 import "dart:math" show max;
 import 'dart:collection';
 
 import 'package:js_runtime/shared/async_await_error_codes.dart'
@@ skipping 1005 matching lines @@
         node.update
       ], (List<js.Expression> transformed) {
         addStatement(new js.For(transformed[0], transformed[1], transformed[2],
              translateInBlock(node.body)));
       });
       insideUntranslatedBreakable = oldInsideUntranslated;
       return;
     }
 
     if (node.init != null) {
-      addExpressionStatement(visitExpression(node.init));
+      visitExpressionIgnoreResult(node.init);
     }
     int startLabel = newLabel("for condition");
     // If there is no update, continuing the loop is the same as going to the
     // start.
     int continueLabel =
         (node.update == null) ? startLabel : newLabel("for update");
     continueLabels[node] = continueLabel;
     int afterLabel = newLabel("after for");
     breakLabels[node] = afterLabel;
     beginLabel(startLabel);
@@ skipping 509 matching lines @@
     beginLabel(afterFinallyLabel);
   }
 
   @override
   visitVariableDeclaration(js.VariableDeclaration node) {
     unreachable(node);
   }
 
   @override
   js.Expression visitVariableDeclarationList(js.VariableDeclarationList node) {
-    List<js.Expression> initializations = new List<js.Expression>();
-
-    // Declaration of local variables is hoisted outside the helper but the
-    // initialization is done here.
     for (js.VariableInitialization initialization in node.declarations) {
       js.VariableDeclaration declaration = initialization.declaration;
       localVariables.add(declaration);
       if (initialization.value != null) {
         withExpression(initialization.value, (js.Expression value) {
-          initializations.add(
+          addExpressionStatement(
               new js.Assignment(new js.VariableUse(declaration.name), value));
         }, store: false);
       }
     }
-    if (initializations.isEmpty) {
-      // Dummy expression. Will be dropped by [visitExpressionIgnoreResult].
-      return js.number(0);
-    } else {
-      return initializations.reduce(
-          (js.Expression first, js.Expression second) {
-        return new js.Binary(",", first, second);
-      });
-    }
+    return js.number(0); // Dummy expression.
   }
 
   @override
   void visitVariableInitialization(js.VariableInitialization node) {
     unreachable(node);
   }
 
   @override
   js.Expression visitVariableUse(js.VariableUse node) {
     Pair<String, String> renaming = variableRenamings.lastWhere(
@@ skipping 1004 matching lines @@
     return condition || body;
   }
 
   @override
   bool visitDartYield(js.DartYield node) {
     hasYield = true;
     visit(node.expression);
     return true;
   }
 }