Make CompilerTask independent of compiler.

site/try/poi/poi.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 trydart.poi;
 
 import 'dart:async' show
     Completer,
     Future;
 
@@ skipping 547 matching lines @@
         printWallClock('Skipped ${work.element}.');
         return;
       }
     }
     f(work);
     printWallClock('Processed ${work.element}.');
   }
 }
 
 class PoiTask extends CompilerTask {
-  PoiTask(Compiler compiler) : super(compiler);
+  PoiTask(Compiler compiler) : super(compiler.measurer);
 
   String get name => 'POI';
 }