Make CompilerTask independent of compiler.

tests/compiler/dart2js/patch_test.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.
 
 import 'dart:async';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/messages.dart' show
     MessageKind;
@@ skipping 188 matching lines @@
         if (expectIsPatched) {
           AstElement patch =
               ensure(compiler, "test", compiler.coreLibrary.patch.find,
                   expectIsPatch: true, checkHasBody: true);
           Expect.equals(origin.patch, patch);
           Expect.equals(patch.origin, origin);
           Expect.equals(patchText, patch.node.toString());
         }
 
         compiler.analyzeElement(origin);
-        compiler.enqueuer.resolution.emptyDeferredTaskQueue();
+        compiler.enqueuer.resolution.emptyDeferredQueueForTesting();
 
         DiagnosticCollector collector = compiler.diagnosticCollector;
         Expect.isTrue(collector.warnings.isEmpty,
                       "Unexpected warnings: ${collector.warnings}");
         if (expectedError != null) {
           Expect.equals(expectedError,
                         collector.errors.first.message.toString());
         } else {
           Expect.isTrue(collector.errors.isEmpty,
                         "Unexpected errors: ${collector.errors}");
@@ skipping 890 matching lines @@
     await testPatchNonFunction();
 
     await testPatchAndSelector();
 
     await testEffectiveTarget();
 
     await testAnalyzeAllInjectedMembers();
     await testTypecheckPatchedMembers();
   });
 }