Avoid using dart:developer from the compiler.

pkg/compiler/lib/src/common/tasks.dart

 // Copyright (c) 2012, 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.common.tasks;
 
-import 'dart:developer' show
-    UserTag;
-
 import '../common.dart';
 import '../compiler.dart' show
     Compiler;
 import '../elements/elements.dart' show
     Element;
 
 typedef void DeferredAction();
 
 class DeferredTask {
   final Element element;
   final DeferredAction action;
 
   DeferredTask(this.element, this.action);
 }
 
 class CompilerTask {
   final Compiler compiler;
   final Stopwatch watch;
-  UserTag profilerTag;
   final Map<String, GenericTask> _subtasks = <String, GenericTask>{};
 
   CompilerTask(Compiler compiler)
       : this.compiler = compiler,
         watch = (compiler.verbose) ? new Stopwatch() : null;
 
   DiagnosticReporter get reporter => compiler.reporter;
 
   String get name => "Unknown task '${this.runtimeType}'";
 
   int get timing {
     if (watch == null) return 0;
     int total = watch.elapsedMilliseconds;
     for (GenericTask subtask in _subtasks.values) {
       total += subtask.timing;
     }
     return total;
   }
 
-  UserTag getProfilerTag() {
-    if (profilerTag == null) profilerTag = new UserTag(name);
-    return profilerTag;
-  }
-
   measure(action()) {
     // In verbose mode when watch != null.
     if (watch == null) return action();
     CompilerTask previous = compiler.measuredTask;
     if (identical(this, previous)) return action();
     compiler.measuredTask = this;
     if (previous != null) previous.watch.stop();
     watch.start();
-    UserTag oldTag = getProfilerTag().makeCurrent();
     try {
       return action();
     } finally {
       watch.stop();
-      oldTag.makeCurrent();
       if (previous != null) previous.watch.start();
       compiler.measuredTask = previous;
     }
   }
 
   measureElement(Element element, action()) {
     reporter.withCurrentElement(element, () => measure(action));
   }
 
   /// Measure the time spent in [action] (if in verbose mode) and accumulate it
@@ skipping 12 matching lines @@
 
   int getSubtaskTime(String subtask) => _subtasks[subtask].timing;
 }
 
 class GenericTask extends CompilerTask {
   final String name;
 
   GenericTask(this.name, Compiler compiler)
       : super(compiler);
 }