Remove BlockExpression from the Kernel language.

lib/type_propagation/builder.dart

 // Copyright (c) 2016, 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 kernel.type_propagation.builder;
 
 import '../ast.dart';
 import '../class_hierarchy.dart';
 import '../core_types.dart';
 import 'canonicalizer.dart';
 import 'constraints.dart';
@@ skipping 1480 matching lines @@
   int visitNullLiteral(NullLiteral node) {
     return builder.nullNode;
   }
 
   int visitLet(Let node) {
     environment.localVariables[node.variable] =
         build(node.variable.initializer);
     return build(node.body);
   }
 
-  int visitBlockExpression(BlockExpression node) {
-    statementBuilder.build(node.body);
-    return build(node.value);
-  }
-
   int buildInnerFunction(FunctionNode node, {VariableDeclaration self}) {
     int variable = builder.newFunction(node);
     if (self != null) {
       assert(!environment.localVariables.containsKey(self));
       environment.localVariables[self] = variable;
     }
     Environment inner = new Environment.inner(environment);
     builder.buildFunctionNode(node, inner, function: variable);
     return variable;
   }
@@ skipping 456 matching lines @@
         environment.addStore(input, field, argument);
       }
     }
     for (int arity = minArity; arity <= maxArity; ++arity) {
       int returnLocation =
           environment.getLoad(input, fieldNames.getReturnField(arity));
       visitContravariant(node.returnType, returnLocation);
     }
   }
 }