Make CompilerTask independent of compiler.

pkg/dart2js_incremental/lib/caching_compiler.dart

 // Copyright (c) 2013, 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 dart2js_incremental;
 
 /// Do not call this method directly. It will be made private.
 // TODO(ahe): Make this method private.
 Future<CompilerImpl> reuseCompiler(
     {CompilerDiagnostics diagnosticHandler,
@@ skipping 69 matching lines @@
       return compiler.libraryLoader.loadLibrary(core).then((_) {
         // Likewise, always be prepared for runtimeType support.
         // TODO(johnniwinther): Add global switch to force RTI.
         compiler.enabledRuntimeType = true;
         backend.registerRuntimeType(
             compiler.enqueuer.resolution, compiler.globalDependencies);
         return compiler;
       });
     });
   } else {
-    for (final task in compiler.tasks) {
-      if (task.watch != null) {
-        task.watch.reset();
-      }
-    }
+    compiler.tasks.forEach((t) => t.clearMeasurements());
     compiler
         ..userOutputProvider = outputProvider
         ..provider = inputProvider
         ..handler = diagnosticHandler
         ..enqueuer.resolution.queueIsClosed = false
         ..enqueuer.resolution.hasEnqueuedReflectiveElements = false
         ..enqueuer.resolution.hasEnqueuedReflectiveStaticFields = false
         ..enqueuer.codegen.queueIsClosed = false
         ..enqueuer.codegen.hasEnqueuedReflectiveElements = false
         ..enqueuer.codegen.hasEnqueuedReflectiveStaticFields = false
@@ skipping 86 matching lines @@
   final Map<String, String> output = new Map<String, String>();
 
   EventSink<String> createEventSink(String name, String extension) {
     return new StringEventSink((String data) {
       output['$name.$extension'] = data;
     });
   }
 
   String operator[] (String key) => output[key];
 }