Make CompilerTask independent of compiler.

pkg/compiler/lib/src/dart_backend/backend.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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 439 matching lines @@
 /// [ConstantCompilerTask] for compilation of constants for the Dart backend.
 ///
 /// Since this task needs no distinction between frontend and backend constants
 /// it also serves as the [BackendConstantEnvironment].
 class DartConstantTask extends ConstantCompilerTask
     implements BackendConstantEnvironment {
   final DartConstantCompiler constantCompiler;
 
   DartConstantTask(Compiler compiler)
       : this.constantCompiler = new DartConstantCompiler(compiler),
-        super(compiler);
+        super(compiler.measurer);
 
   String get name => 'ConstantHandler';
 
   @override
   ConstantSystem get constantSystem => constantCompiler.constantSystem;
 
   @override
   bool hasConstantValue(ConstantExpression expression) {
     return constantCompiler.hasConstantValue(expression);
   }
@@ skipping 63 matching lines @@
   }
 
   // TODO(johnniwinther): Remove this when values are computed from the
   // expressions.
   @override
   void copyConstantValues(DartConstantTask task) {
     constantCompiler.constantValueMap
         .addAll(task.constantCompiler.constantValueMap);
   }
 }