Throw and a small fix to If.

frog/leg/ssa/tracer.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class HTracer extends HGraphVisitor {
   int indent = 0;
   final StringBuffer output;
 
   factory HTracer.singleton() {
     if (_singleton === null) _singleton = new HTracer._internal();
@@ skipping 174 matching lines @@
   String visitParameter(HParameter node) => "p${node.parameterIndex}";
 
   String visitPhi(HPhi phi) {
     return "Phi(${temporaryId(phi.inputs[0])}, ${temporaryId(phi.inputs[1])})";
   }
 
   String visitReturn(HReturn node) => "Return ${temporaryId(node.inputs[0])}";
 
   String visitSubtract(HSubtract node) => visitInvoke(node);
 
+  String visitThrow(HThrow node) => "Throw ${temporaryId(node.inputs[0])}";
+
   String visitTruncatingDivide(HTruncatingDivide node) => visitInvoke(node);
 }