Added Scrollable.scrollTo()

sky/framework/components/scrollable.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import '../animation/generators.dart';
 import '../animation/mechanics.dart';
 import '../animation/scroll_behavior.dart';
 import '../fn.dart';
 import '../theme/view-configuration.dart' as config;
 import 'dart:math' as math;
@@ skipping 25 matching lines @@
       onPointerDown: _handlePointerDown,
       onPointerUp: _handlePointerUpOrCancel,
       onPointerCancel: _handlePointerUpOrCancel,
       onGestureFlingStart: _handleFlingStart,
       onGestureFlingCancel: _handleFlingCancel,
       onGestureScrollUpdate: _handleScrollUpdate,
       onWheel: _handleWheel
     );
   }
 
-  bool scrollBy(double scrollDelta) {
-    var newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
+  bool scrollTo(double newScrollOffset) {
     if (newScrollOffset == _scrollOffset)
       return false;
     setState(() {
       _scrollOffset = newScrollOffset;
     });
     return true;
   }
 
+  bool scrollBy(double scrollDelta) {
+    var newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
+    return scrollTo(newScrollOffset);
+  }
+
   void _stopSimulation() {
     if (_simulation == null)
       return;
     _simulation.cancel();
     _simulation = null;
   }
 
   void _startSimulation(Particle particle) {
     _stopSimulation();
     _simulation = scrollBehavior.release(particle);
@@ skipping 28 matching lines @@
   }
 
   void _handleFlingCancel(sky.GestureEvent event) {
     _startSimulation(_createParticle());
   }
 
   void _handleWheel(sky.WheelEvent event) {
     scrollBy(-event.offsetY);
   }
 }