cps-ir: Support foreign code.

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 cb1659b7688752adac610386e3bb7b72f693026b..cb1da7cbad259e5445aafb36809d79f5546167c1 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -172,6 +172,10 @@ class BlockCollector extends StatementVisitor {
     _addStatement(node);
     visitStatement(node.next);
   }
+
+  visitForeignStatement(ForeignStatement node) {
+    _addStatement(node);
+  }
 }
 
 class TreeTracer extends TracerUtil with StatementVisitor {
@@ -321,6 +325,11 @@ class TreeTracer extends TracerUtil with StatementVisitor {
   String expr(Expression e) {
     return e.accept(new SubexpressionVisitor(names));
   }
+
+  @override
+  visitForeignStatement(ForeignStatement node) {
+    printStatement(null, 'foreign');
+  }
 }
 
 class SubexpressionVisitor extends ExpressionVisitor<String> {
@@ -509,6 +518,12 @@ class SubexpressionVisitor extends ExpressionVisitor<String> {
     String args = node.arguments.map(visitExpression).join(', ');
     return 'CreateInvocationMirror(${node.selector.name}, $args)';
   }
+
+  @override
+  String visitForeignExpression(ForeignExpression node) {
+    String arguments = node.arguments.map(visitExpression).join(', ');
+    return 'Foreign "${node.codeTemplate}"($arguments)';
+  }
 }
 
 /**