Fix uses_bottom_as_dynamic ("fuzzy arrow") errors for ACX model libraries.

Using dynamic as bottom will become an error in Dart 2.0. dart-lang/sdk#29630

PiperOrigin-RevId: 182013886

Author: srawlins

lib/model/selection/tree_selection_options.dart

@@ -35,7 +35,7 @@ class TreeSelectionOptions<T> extends SelectionOptions<T>
       : _itemRenderer = itemRenderer ?? defaultItemRenderer,
         _itemsOptions = new Map<T, TreeSelectionOptionData<T>>.fromIterable(
             listOfOptions,
-            key: (TreeSelectionOptionData<T> item) => item.value),
+            key: (item) => (item as TreeSelectionOptionData<T>).value),
         super(const []) {
     _comparator = comparator ?? _defaultComparator;
     _parentToChildrenMap = _generateParentToChildrenMap(listOfOptions);

lib/model/ui/item_sorter.dart

@@ -12,10 +12,17 @@ import 'package:angular_components/model/ui/has_renderer.dart';
 /// [itemRenderer] should return a unique string representation for each item.
 List<T> sortItems<T>(ItemRenderer<T> itemRenderer, Iterable<T> items,
     {bool ignoreCase: false}) {
+  // TODO(google): Use new SplayTreeMap<String, T>.fromIterable<T>(...) when
+  // generic constructors becomes available.
+  var itemsMap = new SplayTreeMap<String, T>();
   if (ignoreCase) {
-    return new SplayTreeMap<String, T>.fromIterable(items,
-        key: (T item) => itemRenderer(item).toLowerCase()).values.toList();
+    for (T item in items) {
+      itemsMap[itemRenderer(item).toLowerCase()] = item;
+    }
+  } else {
+    for (T item in items) {
+      itemsMap[itemRenderer(item)] = item;
+    }
   }
-  return new SplayTreeMap<String, T>.fromIterable(items,
-      key: (T item) => itemRenderer(item)).values.toList();
+  return itemsMap.values.toList();
 }