dart2js cps: Support sync* and yield.

pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart
index 5240db91ecc1ba7d9ef1f4ad67522a8b4fe94077..b15f510c3dd7645b764cf94701af496c11831ee8 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_tracer.dart
@@ -397,6 +397,13 @@ class IRTracer extends TracerUtil implements cps_ir.Visitor {
   }
 
   @override
+  visitYield(cps_ir.Yield node) {
+    String value = formatReference(node.input);
+    String continuation = formatReference(node.continuation);
+    return 'Yield $value $continuation';
+  }
+
+  @override
   visitRefinement(cps_ir.Refinement node) {
     String value = formatReference(node.value);
     return 'Refinement $value ${node.type}';
@@ -675,9 +682,15 @@ class BlockCollector implements cps_ir.Visitor {
 
   @override
   visitAwait(cps_ir.Await node) {
-    unexpectedNode(node);
+    addEdgeToContinuation(node.continuation);
+  }
+
+  @override
+  visitYield(cps_ir.Yield node) {
+    addEdgeToContinuation(node.continuation);
   }
 
+  @override
   visitRefinement(cps_ir.Refinement node) {
     unexpectedNode(node);
   }