Add support for fields to the new dart backend.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

 // Copyright (c) 2014, 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 tree_ir.optimization;
 
 /**
  * Performs the following transformations on the tree:
  * - Assignment propagation
  * - If-to-conditional conversion
@@ skipping 89 matching lines @@
   /// for a break to L' if L maps to L'.
   Map<Label, Jump> labelRedirects = <Label, Jump>{};
 
   /// Returns the redirect target of [label] or [label] itself if it should not
   /// be redirected.
   Jump redirect(Jump jump) {
     Jump newJump = labelRedirects[jump.target];
     return newJump != null ? newJump : jump;
   }
 
-  void rewrite(FunctionDefinition definition) {
+  void rewrite(ExecutableDefinition definition) => definition.acceptPass(this);
+
+  void rewriteFieldDefinition(FieldDefinition definition) {
+    environment = <Assign>[];
+    definition.body = visitStatement(definition.body);
+
+    // TODO(kmillikin):  Allow definitions that are not propagated.  Here,
+    // this means rebuilding the binding with a recursively unnamed definition,
+    // or else introducing a variable definition and an assignment.
+    assert(environment.isEmpty);
+  }
+
+  void rewriteFunctionDefinition(FunctionDefinition definition) {
     if (definition.isAbstract) return;
 
     environment = <Assign>[];
     definition.body = visitStatement(definition.body);
 
     // TODO(kmillikin):  Allow definitions that are not propagated.  Here,
     // this means rebuilding the binding with a recursively unnamed definition,
     // or else introducing a variable definition and an assignment.
     assert(environment.isEmpty);
   }
 
+
   Expression visitExpression(Expression e) => e.processed ? e : e.accept(this);
 
   Expression visitVariable(Variable node) {
     // Propagate a variable's definition to its use site if:
     // 1.  It has a single use, to avoid code growth and potential duplication
     //     of side effects, AND
     // 2.  It was the most recent expression evaluated so that we do not
     //     reorder expressions with side effects.
     if (!environment.isEmpty &&
         environment.last.variable == node &&
@@ skipping 410 matching lines @@
   }
 
   Expression makeCondition(Expression e, bool polarity) {
     return polarity ? e : new Not(e);
   }
 
   Statement getBranch(If node, bool polarity) {
     return polarity ? node.thenStatement : node.elseStatement;
   }
 }