Add widget of the week videos (#102862)

packages/flutter/lib/src/material/dropdown.dart

@@ -784,6 +784,8 @@ class DropdownButtonHideUnderline extends InheritedWidget {
 /// shows the currently selected item as well as an arrow that opens a menu for
 /// selecting another item.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=ZzQ_PWrFihg}
+///
 /// One ancestor must be a [Material] widget and typically this is
 /// provided by the app's [Scaffold].
 ///

packages/flutter/lib/src/material/flutter_logo.dart

@@ -7,6 +7,8 @@ import 'package:flutter/widgets.dart';
 /// The Flutter logo, in widget form. This widget respects the [IconTheme].
 /// For guidelines on using the Flutter logo, visit https://flutter.dev/brand.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=aAmP-WcI6dg}
+///
 /// See also:
 ///
 ///  * [IconTheme], which provides ambient configuration for icons.

packages/flutter/lib/src/material/scaffold.dart

@@ -62,6 +62,8 @@ enum _ScaffoldSlot {
 
 /// Manages [SnackBar]s and [MaterialBanner]s for descendant [Scaffold]s.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=lytQi-slT5Y}
+///
 /// This class provides APIs for showing snack bars and material banners at the
 /// bottom and top of the screen, respectively.
 ///

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

@@ -5319,6 +5319,8 @@ class Wrap extends MultiChildRenderObjectWidget {
 /// A widget that sizes and positions children efficiently, according to the
 /// logic in a [FlowDelegate].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=NG6pvXpnIso}
+///
 /// Flow layouts are optimized for repositioning children using transformation
 /// matrices.
 ///
@@ -6409,6 +6411,8 @@ class MouseRegion extends SingleChildRenderObjectWidget {
 
 /// A widget that creates a separate display list for its child.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=cVAGLDuc2xE}
+///
 /// This widget creates a separate display list for its child, which
 /// can improve performance if the subtree repaints at different times than
 /// the surrounding parts of the tree.
@@ -7408,6 +7412,8 @@ typedef StatefulWidgetBuilder = Widget Function(BuildContext context, StateSette
 
 /// A platonic widget that both has state and calls a closure to obtain its child widget.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=syvT63CosNE}
+///
 /// The [StateSetter] function passed to the [builder] is used to invoke a
 /// rebuild instead of a typical [State]'s [State.setState].
 ///

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

@@ -997,6 +997,8 @@ class HeroController extends NavigatorObserver {
 
 /// Enables or disables [Hero]es in the widget subtree.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=AaIASk2u1C0}
+///
 /// When [enabled] is false, all [Hero] widgets in this subtree will not be
 /// involved in hero animations.
 ///