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

pkg/compiler/lib/src/tree_ir/tree_ir_nodes.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_nodes;
 
 import '../constants/expressions.dart';
 import '../constants/values.dart' as values;
 import '../dart_types.dart' show DartType, InterfaceType, TypeVariableType;
 import '../elements/elements.dart';
@@ skipping 677 matching lines @@
 
   accept(ExpressionVisitor visitor) => visitor.visitCreateInstance(this);
   accept1(ExpressionVisitor1 visitor, arg) {
     return visitor.visitCreateInstance(this, arg);
   }
 }
 
 class GetField extends Expression {
   Expression object;
   Element field;
+  bool objectIsNotNull;
 
-  GetField(this.object, this.field);
+  GetField(this.object, this.field, {this.objectIsNotNull: false});
 
   accept(ExpressionVisitor visitor) => visitor.visitGetField(this);
   accept1(ExpressionVisitor1 visitor, arg) => visitor.visitGetField(this, arg);
 }
 
 class SetField extends Expression {
   Expression object;
   Element field;
   Expression value;
 
@@ skipping 742 matching lines @@
 
   /// Number of uses of the current fallthrough target.
   int get useCount => _stack.last.useCount;
 
   /// Indicate that a statement will fall through to the current fallthrough
   /// target.
   void use() {
     ++_stack.last.useCount;
   }
 }