Update webview_flutter.dart

packages/webview_flutter/lib/webview_flutter.dart

@@ -211,7 +211,11 @@ class WebView extends StatefulWidget {
 
   /// The initial URL to load.
   final String initialUrl;
+
+  /// The initial baseURL to load.
   final String baseUrl;
+
+  /// The initial static html to load.
   final String html;
 
   /// Whether Javascript execution is enabled.
@@ -554,7 +558,12 @@ class WebViewController {
     return _webViewPlatformController.loadUrl(url, headers);
   }
 
+  /// Loads the specified html.
+  ///
+  /// `html` must not be null.
+  ///
   Future<void> loadHtml(String html) async {
+    assert(html != null);
     return _webViewPlatformController.loadHtml(html);
   }