Fix a bug in the way we deal with HTypeKnown instructions in our SSA type propagation phase.

sdk/lib/_internal/compiler/implementation/ssa/tracer.dart

 // Copyright (c) 2013, 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.
 
 library tracer;
 
 import 'dart:async' show EventSink;
 
 import 'ssa.dart';
 import '../js_backend/js_backend.dart';
@@ skipping 156 matching lines @@
   }
 }
 
 class HInstructionStringifier implements HVisitor<String> {
   final Compiler compiler;
   final JavaScriptItemCompilationContext context;
   final HBasicBlock currentBlock;
 
   HInstructionStringifier(this.context, this.currentBlock, this.compiler);
 
-  visit(HInstruction node) => node.accept(this);
+  visit(HInstruction node) => '${node.accept(this)} ${node.instructionType}';
 
   String temporaryId(HInstruction instruction) {
     String prefix;
     HType type = instruction.instructionType;
     if (type.isNull()) {
       prefix = 'u';
     } else if (type.isConflicting()) {
       prefix = 'c';
     } else if (type.isExtendableArray(compiler)) {
       prefix = 'e';
@@ skipping 327 matching lines @@
 
   String visitTypeKnown(HTypeKnown node) {
     assert(node.inputs.length == 1);
     return "TypeKnown: ${temporaryId(node.checkedInput)} is ${node.knownType}";
   }
 
   String visitRangeConversion(HRangeConversion node) {
     return "RangeConversion: ${node.checkedInput}";
   }
 }