Switch to Iterable.cast instance method (flutter#150185)

Switch away from the `Iterable.castFrom` static method to the `Iterable.cast` instance method which is more readable and more consistent with other iterable usages.

Author: parlough

packages/flutter/lib/src/widgets/nested_scroll_view.dart

@@ -1209,8 +1209,7 @@ class _NestedScrollController extends ScrollController {
   }
 
   Iterable<_NestedScrollPosition> get nestedPositions {
-    // TODO(vegorov): use instance method version of castFrom when it is available.
-    return Iterable.castFrom<ScrollPosition, _NestedScrollPosition>(positions);
+    return positions.cast<_NestedScrollPosition>();
   }
 }
 

packages/flutter_driver/lib/src/driver/timeline.dart

@@ -111,11 +111,11 @@ List<TimelineEvent>? _parseEvents(Map<String, dynamic> json) {
     return null;
   }
 
-  final List<TimelineEvent> timelineEvents =
-      Iterable.castFrom<dynamic, Map<String, dynamic>>(jsonEvents)
-          .map<TimelineEvent>(
-              (Map<String, dynamic> eventJson) => TimelineEvent(eventJson))
-          .toList();
+  final List<TimelineEvent> timelineEvents = jsonEvents
+      .cast<Map<String, dynamic>>()
+      .map<TimelineEvent>(
+          (Map<String, dynamic> eventJson) => TimelineEvent(eventJson))
+      .toList();
 
   timelineEvents.sort((TimelineEvent e1, TimelineEvent e2) {
     return switch ((e1.timestampMicros, e2.timestampMicros)) {