dart2js cps: Share interceptors by default and propagate to use later.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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_builder;
 
 import '../dart2jslib.dart' as dart2js;
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../util/util.dart' show CURRENT_ELEMENT_SPANNABLE;
@@ skipping 247 matching lines @@
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node');
   }
 
   Statement visitSetField(cps_ir.SetField node) {
     return new ExpressionStatement(
         new SetField(getVariableUse(node.object),
                      node.field,
                      getVariableUse(node.value)),
         visit(node.body));
   }
-
+  
   Expression visitInterceptor(cps_ir.Interceptor node) {
     return new Interceptor(getVariableUse(node.input), node.interceptedClasses);
   }
 
   Expression visitCreateInstance(cps_ir.CreateInstance node) {
     return new CreateInstance(
         node.classElement,
         translateArguments(node.arguments),
         translateArguments(node.typeInformation),
         node.sourceInformation);
   }
 
   Expression visitGetField(cps_ir.GetField node) {
-    return new GetField(getVariableUse(node.object), node.field);
+    return new GetField(getVariableUse(node.object), node.field,
+        objectIsNotNull: node.objectIsNotNull);
   }
 
   Expression visitCreateBox(cps_ir.CreateBox node) {
     return new CreateBox();
   }
 
   visitCreateInvocationMirror(cps_ir.CreateInvocationMirror node) {
     return new CreateInvocationMirror(
         node.selector,
         translateArguments(node.arguments));
@@ skipping 338 matching lines @@
                         getVariableUse(node.index));
   }
 
   Expression visitSetIndex(cps_ir.SetIndex node) {
     return new SetIndex(getVariableUse(node.object),
                         getVariableUse(node.index),
                         getVariableUse(node.value));
   }
 }