Allow view to resize its root node.

lib/web_ui/lib/src/engine/platform_dispatcher.dart

@@ -773,7 +773,10 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
     scheduleFrameCallback!();
   }
 
-  /// Updates the application's rendering on the GPU with the newly provided
+  /// Updates the [view]'s rendering on the GPU with the newly provided [scene]
+  /// of physical [size].
+  ///
+  /// This function must be called within the scope of the
   /// [Scene]. This function must be called within the scope of the
   /// [onBeginFrame] or [onDrawFrame] callbacks being invoked. If this function
   /// is called a second time during a single [onBeginFrame]/[onDrawFrame]
@@ -797,27 +800,27 @@ class EnginePlatformDispatcher extends ui.PlatformDispatcher {
   ///    scheduling of frames.
   ///  * [RendererBinding], the Flutter framework class which manages layout and
   ///    painting.
-  @override
-  Future<void> render(ui.Scene scene, [ui.FlutterView? view]) async {
-    assert(view != null || implicitView != null,
-        'Calling render without a FlutterView');
-    if (view == null && implicitView == null) {
+  Future<void> render(ui.Scene scene, {
+      ui.FlutterView? view,
+  }) async {
+    final EngineFlutterView? target = (view ?? implicitView) as EngineFlutterView?;
+    assert(target != null, 'Calling render without a FlutterView');
+    if (target == null) {
       // If there is no view to render into, then this is a no-op.
       return;
     }
-    final ui.FlutterView viewToRender = view ?? implicitView!;
 
     // Only render in an `onDrawFrame` or `onBeginFrame` scope. This is checked
     // by checking if the `_viewsRenderedInCurrentFrame` is non-null and this
     // view hasn't been rendered already in this scope.
     final bool shouldRender =
-        _viewsRenderedInCurrentFrame?.add(viewToRender) ?? false;
+        _viewsRenderedInCurrentFrame?.add(target) ?? false;
     // TODO(harryterkelsen): HTML renderer needs to violate the render rule in
     // order to perform golden tests in Flutter framework because on the HTML
     // renderer, golden tests render to DOM and then take a browser screenshot,
     // https://github.com/flutter/flutter/issues/137073.
     if (shouldRender || renderer.rendererTag == 'html') {
-      await renderer.renderScene(scene, viewToRender);
+      await renderer.renderScene(scene, target);
     }
   }
 

lib/web_ui/lib/src/engine/window.dart

@@ -117,8 +117,7 @@ base class EngineFlutterView implements ui.FlutterView {
   @override
   void render(ui.Scene scene, {ui.Size? size}) {
     assert(!isDisposed, 'Trying to render a disposed EngineFlutterView.');
-    // TODO(goderbauer): Respect the provided size when "physicalConstraints" are not always tight. See TODO on "physicalConstraints".
-    platformDispatcher.render(scene, this);
+    platformDispatcher.render(scene, view: this, size: size);
   }
 
   @override
@@ -156,6 +155,13 @@ base class EngineFlutterView implements ui.FlutterView {
     return _physicalSize ??= _computePhysicalSize();
   }
 
+  void resize(ui.Size newPhysicalSize) {
+    final ui.Size logicalSize = newPhysicalSize / devicePixelRatio;
+    dom.rootElement.style
+      ..width = '${logicalSize.width}px'
+      ..height = '${logicalSize.height}px';
+  }
+
   /// Lazily populated and cleared at the end of the frame.
   ui.Size? _physicalSize;