Remove one more use of mirrors: Components now have to explicitly sync their fields.

This also removes one bit of magic to make it more obvious what on is
going on during a sync, which should hopefully help.

Components have to decide if they support being stateful or not. If
they do, then they must implement syncFields() and have mutable
fields; if they don't, then they must have final fields. This isn't
particularly enforced, though.

This also renames _willSync() to _retainStatefulNodeIfPossible(), for
clarity, and fixes some minor style issues and one typo that was
breaking the drawer.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1174023003

examples/stocks2/lib/stock_app.dart

@@ -46,6 +46,8 @@ class StocksApp extends App {
     _drawerController = new DrawerController(_handleDrawerStatusChanged);
   }
 
+  void syncFields(StocksApp source) { }
+
   bool _isSearching = false;
   String _searchQuery;
 

examples/stocks2/lib/stock_arrow.dart

@@ -12,10 +12,11 @@ import 'dart:math' as math;
 import 'dart:sky' as sky;
 
 class StockArrow extends Component {
-  double percentChange;
 
   StockArrow({ Object key, this.percentChange }) : super(key: key);
 
+  final double percentChange;
+
   int _colorIndexForPercentChange(double percentChange) {
     double maxPercent = 10.0;
     double normalizedPercentChange = math.min(percentChange.abs(), maxPercent) / maxPercent;
@@ -71,4 +72,5 @@ class StockArrow extends Component {
         height: size,
         margin: const EdgeDims.symmetric(horizontal: 5.0));
   }
+
 }

examples/stocks2/lib/stock_list.dart

@@ -8,8 +8,6 @@ import 'stock_data.dart';
 import 'stock_row.dart';
 
 class Stocklist extends FixedHeightScrollable {
-  String query;
-  List<Stock> stocks;
 
   Stocklist({
     Object key,
@@ -17,6 +15,15 @@ class Stocklist extends FixedHeightScrollable {
     this.query
   }) : super(itemHeight: StockRow.kHeight, key: key);
 
+  String query;
+  List<Stock> stocks;
+
+  void syncFields(Stocklist source) {
+    query = source.query;
+    stocks = source.stocks;
+    super.syncFields(source);
+  }
+
   List<UINode> buildItems(int start, int count) {
     var filteredStocks = stocks.where((stock) {
       return query == null ||

examples/stocks2/lib/stock_menu.dart

@@ -8,10 +8,15 @@ import 'package:sky/framework/components2/checkbox.dart';
 import 'package:sky/framework/theme/view_configuration.dart';
 
 class StockMenu extends Component {
-  PopupMenuController controller;
 
-  StockMenu({Object key, this.controller, this.autorefresh: false, this.onAutorefreshChanged}) : super(key: key);
+  StockMenu({
+    Object key,
+    this.controller,
+    this.autorefresh: false,
+    this.onAutorefreshChanged
+  }) : super(key: key);
 
+  final PopupMenuController controller;
   final bool autorefresh;
   final ValueChanged onAutorefreshChanged;
 

examples/stocks2/lib/stock_row.dart

@@ -12,13 +12,12 @@ import 'stock_arrow.dart';
 import 'stock_data.dart';
 
 class StockRow extends Component {
-  static const double kHeight = 70.0;
 
-  Stock stock;
+  StockRow({ Stock stock }) : this.stock = stock, super(key: stock.symbol);
 
-  StockRow({ Stock stock }) : super(key: stock.symbol) {
-    this.stock = stock;
-  }
+  final Stock stock;
+
+  static const double kHeight = 70.0;
 
   UINode build() {
     String lastSale = "\$${stock.lastSale.toStringAsFixed(2)}";