Add widget of the week videos to documentation (#61368)

packages/flutter/lib/src/cupertino/action_sheet.dart

@@ -77,6 +77,8 @@ const double _kDividerThickness = 1.0;
 
 /// An iOS-style action sheet.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=U-ao8p4A82k}
+///
 /// An action sheet is a specific style of alert that presents the user
 /// with a set of two or more choices related to the current context.
 /// An action sheet can have a title, an additional message, and a list

packages/flutter/lib/src/cupertino/activity_indicator.dart

@@ -20,6 +20,8 @@ const Color _kActiveTickColor = CupertinoDynamicColor.withBrightness(
 
 /// An iOS-style activity indicator that spins clockwise.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=AENVH-ZqKDQ}
+///
 /// See also:
 ///
 ///  * <https://developer.apple.com/ios/human-interface-guidelines/controls/progress-indicators/#activity-indicators>

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

@@ -313,6 +313,8 @@ const double _textVerticalSeparation = 18.0;
 ///
 /// To show an [AboutDialog], use [showAboutDialog].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=YFCSODyFxbE}
+///
 /// If the application has a [Drawer], the [AboutListTile] widget can make the
 /// process of showing an about dialog simpler.
 ///

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

@@ -19,6 +19,8 @@ import 'theme_data.dart';
 /// The entire list tile is interactive: tapping anywhere in the tile toggles
 /// the checkbox.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=RkSqPAn9szs}
+///
 /// The [value], [onChanged], [activeColor] and [checkColor] properties of this widget are
 /// identical to the similarly-named properties on the [Checkbox] widget.
 ///

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

@@ -21,6 +21,8 @@ import 'theme.dart';
 /// To create a divider between [ListTile] items, consider using
 /// [ListTile.divideTiles], which is optimized for this case.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=_liUC641Nmk}
+///
 /// The box's total height is controlled by [height]. The appropriate
 /// padding is automatically computed from the height.
 ///

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

@@ -51,6 +51,8 @@ const Duration _kBaseSettleDuration = Duration(milliseconds: 246);
 /// A material design panel that slides in horizontally from the edge of a
 /// [Scaffold] to show navigation links in an application.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=WRj86iHihgY}
+///
 /// Drawers are typically used with the [Scaffold.drawer] property. The child of
 /// the drawer is usually a [ListView] whose first child is a [DrawerHeader]
 /// that displays status information about the current user. The remaining

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

@@ -206,6 +206,8 @@ class _LinearProgressIndicatorPainter extends CustomPainter {
 
 /// A material design linear progress indicator, also known as a progress bar.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=O-rhXZLtpv0}
+///
 /// A widget that shows progress along a line. There are two kinds of linear
 /// progress indicators:
 ///
@@ -397,6 +399,8 @@ class _CircularProgressIndicatorPainter extends CustomPainter {
 /// A material design circular progress indicator, which spins to indicate that
 /// the application is busy.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=O-rhXZLtpv0}
+///
 /// A widget that shows progress along a circle. There are two kinds of circular
 /// progress indicators:
 ///

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

@@ -143,6 +143,8 @@ class _SnackBarActionState extends State<SnackBarAction> {
 /// A lightweight message with an optional action which briefly displays at the
 /// bottom of the screen.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=zpO6n_oZWw0}
+///
 /// To display a snack bar, call `Scaffold.of(context).showSnackBar()`, passing
 /// an instance of [SnackBar] that describes the message.
 ///

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

@@ -316,6 +316,8 @@ class _TabControllerScope extends InheritedWidget {
 /// The [TabController] for descendant widgets that don't specify one
 /// explicitly.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=POtoEH-5l40}
+///
 /// [DefaultTabController] is an inherited widget that is used to share a
 /// [TabController] with a [TabBar] or a [TabBarView]. It's used when sharing an
 /// explicitly created [TabController] isn't convenient because the tab bar

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

@@ -568,6 +568,8 @@ class _TabBarScrollController extends ScrollController {
 /// Typically created as the [AppBar.bottom] part of an [AppBar] and in
 /// conjunction with a [TabBarView].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=POtoEH-5l40}
+///
 /// If a [TabController] is not provided, then a [DefaultTabController] ancestor
 /// must be provided instead. The tab controller's [TabController.length] must
 /// equal the length of the [tabs] list and the length of the
@@ -1144,6 +1146,8 @@ class _TabBarState extends State<TabBar> {
 ///
 /// This widget is typically used in conjunction with a [TabBar].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=POtoEH-5l40}
+///
 /// If a [TabController] is not provided, then there must be a [DefaultTabController]
 /// ancestor.
 ///

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

@@ -25,6 +25,8 @@ import 'toggle_buttons_theme.dart';
 /// correlated by their index in the list. The length of [isSelected] has to
 /// match the length of the [children] list.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=kVEguaQWGAY}
+///
 /// ## Customizing toggle buttons
 /// Each toggle's behavior can be configured by the [onPressed] callback, which
 /// can update the [isSelected] list however it wants to.

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

@@ -269,6 +269,8 @@ class Opacity extends SingleChildRenderObjectWidget {
 /// For example, [ShaderMask] can be used to gradually fade out the edge
 /// of a child by using a [new ui.Gradient.linear] mask.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=7sUL66pTQ7Q}
+///
 /// {@tool snippet}
 ///
 /// This example makes the text look like it is on fire:
@@ -706,6 +708,8 @@ class ClipRRect extends SingleChildRenderObjectWidget {
 
 /// A widget that clips its child using an oval.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=vzWWDO6whIM}
+///
 /// By default, inscribes an axis-aligned oval into its layout dimensions and
 /// prevents its child from painting outside that oval, but the size and
 /// location of the clip oval can be customized using a custom [clipper].
@@ -775,6 +779,8 @@ class ClipOval extends SingleChildRenderObjectWidget {
 /// painted. The callback returns a path and the widget prevents the
 /// child from painting outside the path.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=oAUebVIb-7s}
+///
 /// Clipping to a path is expensive. Certain shapes have more
 /// optimized widgets:
 ///
@@ -1576,6 +1582,8 @@ class RotatedBox extends SingleChildRenderObjectWidget {
 
 /// A widget that insets its child by the given padding.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=oD5RtLhhubg}
+///
 /// When passing layout constraints to its child, padding shrinks the
 /// constraints by the given padding, causing the child to layout at a smaller
 /// size. Padding then sizes itself to its child's size, inflated by the
@@ -6371,6 +6379,8 @@ class RepaintBoundary extends SingleChildRenderObjectWidget {
 
 /// A widget that is invisible during hit testing.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=qV9pqHWxYgI}
+///
 /// When [ignoring] is true, this widget (and its subtree) is invisible
 /// to hit testing. It still consumes space during layout and paints its child
 /// as usual. It just cannot be the target of located events, because it returns
@@ -7092,6 +7102,8 @@ class KeyedSubtree extends StatelessWidget {
 
 /// A platonic widget that calls a closure to obtain its child widget.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=xXNOkIuSYuA}
+///
 /// See also:
 ///
 ///  * [StatefulBuilder], a platonic widget which also has state.

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

@@ -233,6 +233,8 @@ typedef ImageErrorWidgetBuilder = Widget Function(
 
 /// A widget that displays an image.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=7oIAs-0G4mw}
+///
 /// Several constructors are provided for the various ways that an image can be
 /// specified:
 ///

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

@@ -559,6 +559,8 @@ class FixedExtentScrollPhysics extends ScrollPhysics {
 /// This widget is similar to a [ListView] but with the restriction that all
 /// children must be the same size along the scrolling axis.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=dUhmWAz4C7Y}
+///
 /// When the list is at the zero scroll offset, the first child is aligned with
 /// the middle of the viewport. When the list is at the final scroll offset,
 /// the last child is aligned with the middle of the viewport

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

@@ -88,6 +88,8 @@ abstract class Notification {
 
 /// A widget that listens for [Notification]s bubbling up the tree.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=cAnFbFoGM50}
+///
 /// Notifications will trigger the [onNotification] callback only if their
 /// [runtimeType] is a subtype of `T`.
 ///

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

@@ -18,6 +18,8 @@ export 'package:flutter/rendering.dart' show RelativeRect;
 
 /// A widget that rebuilds when the given [Listenable] changes value.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=LKKgYpC-EPQ}
+///
 /// [AnimatedWidget] is most commonly used with [Animation] objects, which are
 /// [Listenable], but it can be used with any [Listenable], including
 /// [ChangeNotifier] and [ValueNotifier].

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

@@ -13,6 +13,8 @@ import 'value_listenable_builder.dart';
 /// [Widget] builder that animates a property of a [Widget] to a target value
 /// whenever the target value changes.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=l9uHB8VXZOg}
+///
 /// The type of the animated property ([Color], [Rect], [double], etc.) is
 /// defined via the type of the provided [tween] (e.g. [ColorTween],
 /// [RectTween], [Tween<double>], etc.).