Rationalise hit testing in the new RenderNode world

sky/sdk/lib/framework/app.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 'layout2.dart';
+import 'dart:sky' as sky;
+
+class AppView {
+  RenderView _renderView;
+
+  void _beginFrame(double timeStamp) {
+    RenderNode.flushLayout();
+    _renderView.paintFrame();
+  }
+
+  void _handleEvent(sky.Event event) {
+    if (event is! sky.PointerEvent)
+      return;
+    HitTestResult result = new HitTestResult();
+    _renderView.hitTest(result, x: event.x, y: event.y);
+    result.path.reversed.forEach((RenderNode node) {
+      node.handlePointer(event);
+    });
+  }
+
+  AppView(RenderBox root) {
+    sky.view.setEventCallback(_handleEvent);
+    sky.view.setBeginFrameCallback(_beginFrame);
+
+    _renderView = new RenderView(root: root);
+    _renderView.layout(newWidth: sky.view.width, newHeight: sky.view.height);
+  
+    sky.view.scheduleFrame();
+  }
+}