don't update source property of iOS webview on load if reading local html content (#4468)

Xamarin.Forms.Platform.MacOS/Renderers/WebViewRenderer.cs

@@ -203,6 +203,9 @@ namespace Xamarin.Forms.Platform.MacOS
 				if (Renderer.Control.IsLoading)
 					return;
 
+				if (Renderer.Control.MainFrameUrl == $"file://{NSBundle.MainBundle.BundlePath}/")
+					return;
+
 				Renderer._ignoreSourceChanges = true;
 				Renderer.Element?.SetValueFromRenderer(WebView.SourceProperty, new UrlWebViewSource { Url = Renderer.Control.MainFrameUrl });
 				Renderer._ignoreSourceChanges = false;

Xamarin.Forms.Platform.iOS/Renderers/WebViewRenderer.cs

@@ -220,8 +220,12 @@ namespace Xamarin.Forms.Platform.iOS
 				if (webView.IsLoading)
 					return;
 
-				_renderer._ignoreSourceChanges = true;
 				var url = GetCurrentUrl();
+
+				if (url == $"file://{NSBundle.MainBundle.BundlePath}/")
+					return;
+
+				_renderer._ignoreSourceChanges = true;
 				WebView.SetValueFromRenderer(WebView.SourceProperty, new UrlWebViewSource { Url = url });
 				_renderer._ignoreSourceChanges = false;
 

Xamarin.Forms.Platform.iOS/Renderers/WkWebViewRenderer.cs

@@ -218,8 +218,11 @@ namespace Xamarin.Forms.Platform.iOS
 				if (webView.IsLoading)
 					return;
 
-				_renderer._ignoreSourceChanges = true;
 				var url = GetCurrentUrl();
+				if (url == $"file://{NSBundle.MainBundle.BundlePath}/")
+					return;
+
+				_renderer._ignoreSourceChanges = true;
 				WebView.SetValueFromRenderer(WebView.SourceProperty, new UrlWebViewSource { Url = url });
 				_renderer._ignoreSourceChanges = false;