Make stocksapp.dart almost pass the dart analyzer.

To test:
sky/tools/shelldb analyze sky/examples/stocks-fn/stocksapp.dart

It prints 600+ warnings about the "native" keyword, and after
this change only a couple warnings about missing library names
which I don't fully understand.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/987613002

examples/fn/widgets/fixedheightscrollable.dart

@@ -106,22 +106,22 @@ abstract class FixedHeightScrollable extends Component {
     _scheduleFlingUpdate();
   }
 
-  void _handleScrollUpdate(sky.Event event) {
+  void _handleScrollUpdate(sky.GestureEvent event) {
     _scrollBy(-event.dy);
   }
 
-  void _handleFlingStart(sky.Event event) {
+  void _handleFlingStart(sky.GestureEvent event) {
     setState(() {
       _flingCurve = new FlingCurve(-event.velocityY, event.timeStamp);
       _scheduleFlingUpdate();
     });
   }
 
-  void _handleFlingCancel(sky.Event event) {
+  void _handleFlingCancel(sky.GestureEvent event) {
     _stopFling();
   }
 
-  void _handleWheel(sky.Event event) {
+  void _handleWheel(sky.WheelEvent event) {
     _scrollBy(-event.offsetY);
   }
 }

examples/fn/widgets/material.dart

@@ -33,9 +33,9 @@ abstract class MaterialComponent extends Component {
      ..events.listen('pointerdown', _startSplash);
   }
 
-  sky.ClientRect _getBoundingRect() => getRoot().getBoundingClientRect();
+  sky.ClientRect _getBoundingRect() => (getRoot() as sky.Element).getBoundingClientRect();
 
-  void _startSplash(sky.Event event) {
+  void _startSplash(sky.PointerEvent event) {
     setState(() {
       if (_splashes == null) {
         _splashes = new LinkedHashSet<SplashAnimation>();

examples/stocks-fn/stocksapp.dart

@@ -3,9 +3,7 @@ library stocksapp;
 import '../../framework/fn.dart';
 import '../data/stocks.dart';
 import '../fn/widgets/widgets.dart';
-import 'dart:collection';
 import 'dart:math';
-import 'dart:sky' as sky;
 
 part 'stockarrow.dart';
 part 'stocklist.dart';

framework/fn.dart

@@ -10,7 +10,7 @@ import 'dart:sky' as sky;
 import 'reflect.dart' as reflect;
 
 bool _initIsInCheckedMode() {
-  void testFn(double i) {}
+  String testFn(i) { double d = i; return d.toString(); }
   try {
     testFn('not a double');
   } catch (ex) {
@@ -405,7 +405,6 @@ class Container extends Element {
   String get _tagName => 'div';
 
   static final Container _emptyContainer = new Container();
-
   Element get _emptyElement => _emptyContainer;
 
   Container({
@@ -470,8 +469,11 @@ class Anchor extends Element {
   String get _tagName => 'a';
 
   static final Anchor _emptyAnchor = new Anchor();
+  Element get _emptyElement => _emptyAnchor;
 
   String href;
+  int width;
+  int height;
 
   Anchor({
     Object key,