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

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
index 90456e9c4193559aec08a6d646af1ca4d23c63ca..f59e4849c065129af9eb81e12293b2bff3d03328 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
@@ -265,7 +265,7 @@ class Builder implements cps_ir.Visitor<Node> {
                      getVariableUse(node.value)),
         visit(node.body));
   }
-
+  
   Expression visitInterceptor(cps_ir.Interceptor node) {
     return new Interceptor(getVariableUse(node.input), node.interceptedClasses);
   }
@@ -279,7 +279,8 @@ class Builder implements cps_ir.Visitor<Node> {
   }
 
   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) {