dart2js cps: Use a strictness flag on Branch instead of rewriting.

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

 // Copyright (c) 2014, 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 dart2js.ir_tracer;
 
 import 'dart:async' show EventSink;
 import 'cps_ir_nodes.dart' as cps_ir hide Function;
 import '../tracer.dart';
 
@@ skipping 209 matching lines @@
 
   visitInvokeContinuation(cps_ir.InvokeContinuation node) {
     String dummy = names.name(node);
     String kont = formatReference(node.continuation);
     String args = node.arguments.map(formatReference).join(', ');
     printStmt(dummy, "InvokeContinuation $kont ($args)");
   }
 
   visitBranch(cps_ir.Branch node) {
     String dummy = names.name(node);
-    String condition = visit(node.condition);
+    String condition = formatReference(node.condition);
     String trueCont = formatReference(node.trueContinuation);
     String falseCont = formatReference(node.falseContinuation);
-    printStmt(dummy, "Branch $condition ($trueCont, $falseCont)");
+    String strict = node.isStrictCheck ? "Strict" : "NonStrict";
+    printStmt(dummy, "Branch $condition ($trueCont, $falseCont) $strict");
   }
 
   visitSetMutable(cps_ir.SetMutable node) {
     String variable = names.name(node.variable.definition);
     String value = formatReference(node.value);
     return 'SetMutable $variable := $value';
   }
 
   String formatReference(cps_ir.Reference ref) {
     cps_ir.Definition target = ref.definition;
@@ skipping 15 matching lines @@
   }
 
   visitMutableVariable(cps_ir.MutableVariable node) {
     return "MutableVariable ${names.name(node)}";
   }
 
   visitContinuation(cps_ir.Continuation node) {
     return "Continuation ${names.name(node)}";
   }
 
-  visitIsTrue(cps_ir.IsTrue node) {
-    return "IsTrue(${names.name(node.value.definition)})";
-  }
-
   visitSetField(cps_ir.SetField node) {
     String object = formatReference(node.object);
     String field = node.field.name;
     String value = formatReference(node.value);
     return 'SetField $object.$field = $value';
   }
 
   visitGetField(cps_ir.GetField node) {
     String object = formatReference(node.object);
     String field = node.field.name;
@@ skipping 317 matching lines @@
   }
 
   visitCreateBox(cps_ir.CreateBox node) {
     unexpectedNode(node);
   }
 
   visitCreateInstance(cps_ir.CreateInstance node) {
     unexpectedNode(node);
   }
 
-  visitIsTrue(cps_ir.IsTrue node) {
-    unexpectedNode(node);
-  }
-
   visitInterceptor(cps_ir.Interceptor node) {
     unexpectedNode(node);
   }
 
   visitReadTypeVariable(cps_ir.ReadTypeVariable node) {
     unexpectedNode(node);
   }
 
   visitReifyRuntimeType(cps_ir.ReifyRuntimeType node) {
     unexpectedNode(node);
@@ skipping 46 matching lines @@
   @override
   visitForeignCode(cps_ir.ForeignCode node) {
     addEdgeToContinuation(node.continuation);
   }
 
   @override
   visitAwait(cps_ir.Await node) {
     unexpectedNode(node);
   }
 }