Add support for fields to the new dart backend.

pkg/compiler/lib/src/tracer.dart

Index: pkg/compiler/lib/src/tracer.dart
diff --git a/pkg/compiler/lib/src/tracer.dart b/pkg/compiler/lib/src/tracer.dart
index 32327c3b05eea8016a07a19ff2c41635d7ea3064..ac930ce1ba3da509521dde50eac7a114e3852c5e 100644
--- a/pkg/compiler/lib/src/tracer.dart
+++ b/pkg/compiler/lib/src/tracer.dart
@@ -57,10 +57,10 @@ class Tracer extends TracerUtil {
     if (irObject is ssa.HGraph) {
       new HTracer(output, compiler, context).traceGraph(name, irObject);
     }
-    else if (irObject is cps_ir.FunctionDefinition) {
+    else if (irObject is cps_ir.ExecutableDefinition) {
       new IRTracer(output).traceGraph(name, irObject);
     }
-    else if (irObject is tree_ir.FunctionDefinition) {
+    else if (irObject is tree_ir.ExecutableDefinition) {
       new TreeTracer(output).traceGraph(name, irObject);
     }
   }