Remove some unused dart:sky IDLs

This CL deletes a bunch of unused IDL files and removes some dead code in the
engine.

examples/raw/painting_node.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 'dart:sky';
-
-PaintingNode paintingNode = null;
-Picture draw(int a, int r, int g, int b) {
-  final double devicePixelRatio = view.devicePixelRatio;
-  Size size = new Size(view.width, view.height);
-
-  PictureRecorder recorder = new PictureRecorder();
-  Canvas canvas = new Canvas(recorder, new Rect.fromLTRB(0.0, 0.0, view.width * devicePixelRatio, view.height * devicePixelRatio));
-  canvas.scale(devicePixelRatio, devicePixelRatio);
-  double radius = size.shortestSide * 0.45;
-
-  Paint paint = new Paint()..color = new Color.fromARGB(a, r, g, b);
-  canvas.drawCircle(size.center(Point.origin), radius, paint);
-
-  if (paintingNode == null) {
-    paintingNode = new PaintingNode();
-    Paint innerPaint = new Paint()..color = new Color.fromARGB(a, 255 - r, 255 - g, 255 - b);
-    PictureRecorder innerRecorder = new PictureRecorder();
-    Canvas innerCanvas = new Canvas(innerRecorder, Point.origin & size);
-    innerCanvas.drawCircle(size.center(Point.origin), radius * 0.5, innerPaint);
-
-    paintingNode.setBackingDrawable(innerRecorder.endRecordingAsDrawable());
-  }
-  canvas.drawPaintingNode(paintingNode, Point.origin);
-
-  return recorder.endRecording();
-}
-
-bool handleEvent(Event event) {
-  if (event.type == "pointerdown") {
-    view.picture = draw(255, 0, 0, 255);
-    view.scheduleFrame();
-    return true;
-  }
-
-  if (event.type == "pointerup") {
-    view.picture = draw(255, 0, 255, 0);
-    view.scheduleFrame();
-    return true;
-  }
-
-  return false;
-}
-
-void main() {
-  view.picture = draw(255, 0, 255, 0);
-  view.scheduleFrame();
-
-  view.setEventCallback(handleEvent);
-}

packages/unit/test/engine/attribute_collection_test.dart

-import 'dart:sky';
-
-import 'package:test/test.dart';
-
-void main() {
-  var div;
-  setUp(() {
-    var document = new Document();
-    div = document.createElement("div");
-  });
-
-  test("should get by index", () {
-    div.setAttribute("attr0", "value0");
-    div.setAttribute("attr1", "value1");
-    var attrs = div.getAttributes();
-    expect(attrs.length, equals(2));
-    expect(attrs[0].name, equals("attr0"));
-    expect(attrs[0].value, equals("value0"));
-    expect(attrs[1].name, equals("attr1"));
-    expect(attrs[1].value, equals("value1"));
-  });
-  test("should set by name", () {
-    div.setAttribute("attrName", "value0");
-    expect(div.getAttribute("attrName"), equals("value0"));
-    expect(div.getAttributes()[0].name, equals("attrName"));
-    expect(div.getAttributes()[0].value, equals("value0"));
-    div.setAttribute("attrName", "new value");
-    expect(div.getAttribute("attrName"), equals("new value"));
-    expect(div.getAttributes()[0].name, equals("attrName"));
-    expect(div.getAttributes()[0].value, equals("new value"));
-  });
-  test("should be case sensitive", () {
-    div.setAttribute("attrName", "value0");
-    expect(div.getAttribute("attrname"), isNull);
-    expect(div.getAttribute("attrName"), equals("value0"));
-  });
-  test("should not live update", () {
-    div.setAttribute("attr0", "0");
-    div.setAttribute("attr1", "1");
-    div.setAttribute("attr2", "2");
-    var oldAttributes = div.getAttributes();
-    expect(oldAttributes.length, equals(3));
-    div.removeAttribute("attr1");
-    expect(oldAttributes.length, equals(3));
-    div.setAttribute("attr0", "value0");
-    div.setAttribute("attr2", "value2");
-    var newAttributes = div.getAttributes();
-    expect(newAttributes.length, equals(2));
-    expect(newAttributes[0].name, equals("attr0"));
-    expect(newAttributes[0].value, equals("value0"));
-    expect(newAttributes[1].name, equals("attr2"));
-    expect(newAttributes[1].value, equals("value2"));
-    expect(newAttributes, isNot(equals(oldAttributes)));
-    expect(oldAttributes[0].name, equals("attr0"));
-    expect(oldAttributes[0].value, equals("0"));
-    expect(oldAttributes[1].name, equals("attr1"));
-    expect(oldAttributes[1].value, equals("1"));
-    expect(oldAttributes[2].name, equals("attr2"));
-    expect(oldAttributes[2].value, equals("2"));
-  });
-}