dart2js cps: Support sync* and yield.

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

Index: pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
index 86a24b63116c21a657acfeda6af24f5997fa98de..01b5847cdb3073f8153280f6368fee513bed1c72 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -178,6 +178,11 @@ class BlockCollector extends StatementVisitor {
   visitForeignStatement(ForeignStatement node) {
     _addStatement(node);
   }
+
+  @override
+  visitYield(Yield node) {
+    _addStatement(node);
+  }
 }
 
 class TreeTracer extends TracerUtil with StatementVisitor {
@@ -336,6 +341,11 @@ class TreeTracer extends TracerUtil with StatementVisitor {
   visitForeignStatement(ForeignStatement node) {
     printStatement(null, 'foreign ${node.codeTemplate.source}');
   }
+
+  @override
+  visitYield(Yield node) {
+    printStatement(null, 'yield ${expr(node.input)}');
+  }
 }
 
 class SubexpressionVisitor extends ExpressionVisitor<String> {
@@ -569,6 +579,12 @@ class SubexpressionVisitor extends ExpressionVisitor<String> {
     String value = visitExpression(node.input);
     return 'Await($value)';
   }
+
+  @override
+  String visitYield(Yield node) {
+    String value = visitExpression(node.input);
+    return 'Yield($value)';
+  }
 }
 
 /**