dart2js cps: Do not treat final field reads as effectively constant.

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.
 
 library tree_ir.optimization.statement_rewriter;
 
 import 'optimization.dart' show Pass;
 import '../tree_ir_nodes.dart';
 import '../../io/source_information.dart';
 
@@ skipping 337 matching lines @@
   /// Returns true if [exp] has no side effects and has a constant value within
   /// any given activation of the enclosing method.
   bool isEffectivelyConstant(Expression exp) {
     // TODO(asgerf): Can be made more aggressive e.g. by checking conditional
     // expressions recursively. Determine if that is a valuable optimization
     // and/or if it is better handled at the CPS level.
     return exp is Constant ||
            exp is This ||
            exp is CreateInvocationMirror ||
            exp is GetStatic && exp.element.isFunction ||
-           exp is GetField && exp.objectIsNotNull && exp.field.isFinal ||
            exp is Interceptor ||
            exp is ApplyBuiltinOperator ||
            exp is VariableUse && constantEnvironment.containsKey(exp.variable);
   }
 
   /// True if [node] is an assignment that can be propagated as a constant.
   bool isEffectivelyConstantAssignment(Expression node) {
     return node is Assign &&
            node.variable.writeCount == 1 &&
            isEffectivelyConstant(node.value);
@@ skipping 851 matching lines @@
   VariableUseVisitor(this.callback);
 
   visitVariableUse(VariableUse use) => callback(use);
 
   visitInnerFunction(FunctionDefinition node) {}
 
   static void visit(Expression node, VariableUseCallback callback) {
     new VariableUseVisitor(callback).visitExpression(node);
   }
 }