Support ElementReference.Focus in WebView (#31050)

Author: SteveSandersonMS

src/Components/WebView/WebView/src/PageContext.cs

@@ -42,7 +42,7 @@ public PageContext(
             JSRuntime.AttachToWebView(ipcSender);
 
             var loggerFactory = services.GetRequiredService<ILoggerFactory>();
-            Renderer = new WebViewRenderer(services, dispatcher, ipcSender, loggerFactory);
+            Renderer = new WebViewRenderer(services, dispatcher, ipcSender, loggerFactory, JSRuntime.ElementReferenceContext);
         }
 
         public void Dispose()

src/Components/WebView/WebView/src/Services/WebViewJSRuntime.cs

@@ -8,8 +8,11 @@ internal class WebViewJSRuntime : JSRuntime
     {
         private IpcSender _ipcSender;
 
+        public ElementReferenceContext ElementReferenceContext { get; }
+
         public WebViewJSRuntime()
         {
+            ElementReferenceContext = new WebElementReferenceContext(this);
             JsonSerializerOptions.Converters.Add(
                 new ElementReferenceJsonConverter(
                     new WebElementReferenceContext(this)));

src/Components/WebView/WebView/src/Services/WebViewRenderer.cs

@@ -22,11 +22,13 @@ public WebViewRenderer(
             IServiceProvider serviceProvider,
             Dispatcher dispatcher,
             IpcSender ipcSender,
-            ILoggerFactory loggerFactory) :
+            ILoggerFactory loggerFactory,
+            ElementReferenceContext elementReferenceContext) :
             base(serviceProvider, loggerFactory)
         {
             _dispatcher = dispatcher;
             _ipcSender = ipcSender;
+            ElementReferenceContext = elementReferenceContext;
         }
 
         public override Dispatcher Dispatcher => _dispatcher;