Remove code supporting incremental compilation in dart2js

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:async'
     show Future, Zone, ZoneDelegate, ZoneSpecification, runZoned;
 
 /// Used to measure where time is spent in the compiler.
@@ skipping 170 matching lines @@
     GenericTask subtask =
         _subtasks.putIfAbsent(name, () => new GenericTask(name, measurer));
     return subtask.measure(action);
   }
 
   Iterable<String> get subtasks => _subtasks.keys;
 
   int getSubtaskTime(String subtask) => _subtasks[subtask].timing;
 
   bool getSubtaskIsRunning(String subtask) => _subtasks[subtask].isRunning;
-
-  /// Used by the dart2js_incremental to provide measurements on each
-  /// incremental compile.
-  clearMeasurements() {
-    if (_isDisabled) return;
-    _watch.reset();
-    _subtasks.values.forEach((s) => s.clearMeasurements());
-  }
 }
 
 class GenericTask extends CompilerTask {
   final String name;
   GenericTask(this.name, Measurer measurer) : super(measurer);
 }
 
 class Measurer {
   /// Measures the total runtime from this object was constructed.
   ///
@@ skipping 39 matching lines @@
   }
 
   /// Call this when the eventloop returns control to us.
   void stopAsyncWallClock() {
     if (currentAsyncTask != null) {
       currentAsyncTask._watch.stop();
     }
     asyncWallClock.stop();
   }
 }