OffScreen - Add ChromiumWebBrowser constructor overload with onAfterBrowserCreated delegate

Use the constructor overload as an alternative to the BrowserInitialized event

Follow up to #3552

Author: amaitland

CefSharp.OffScreen/ChromiumWebBrowser.cs

@@ -40,6 +40,12 @@ public partial class ChromiumWebBrowser : IRenderWebBrowser
         /// </summary>
         private bool browserCreated;
 
+        /// <summary>
+        /// Action which is called immediately before the <see cref="BrowserInitialized"/> event after the
+        /// uderlying Chromium Embedded Framework (CEF) browser has been created.
+        /// </summary>
+        private Action<IBrowser> onAfterBrowserCreatedDelegate;
+
         /// <summary>
         /// Gets a value indicating whether this instance is disposed.
         /// </summary>
@@ -159,9 +165,15 @@ public bool IsBrowserInitialized
         /// <param name="browserSettings">The browser settings to use. If null, the default settings are used.</param>
         /// <param name="requestContext">See <see cref="RequestContext" /> for more details. Defaults to null</param>
         /// <param name="automaticallyCreateBrowser">automatically create the underlying Browser</param>
+        /// <param name="onAfterBrowserCreated">
+        /// Use as an alternative to the <see cref="BrowserInitialized"/> event. If the underlying Chromium Embedded Framework (CEF) browser is created successfully,
+        /// this action is guranteed to be called after the browser created where as the <see cref="BrowserInitialized"/> event may be called before
+        /// you have a chance to subscribe to the event as the CEF Browser is created async. (Issue https://github.com/cefsharp/CefSharp/issues/3552).
+        /// </param>
         /// <exception cref="System.InvalidOperationException">Cef::Initialize() failed</exception>
         public ChromiumWebBrowser(HtmlString html, IBrowserSettings browserSettings = null,
-            IRequestContext requestContext = null, bool automaticallyCreateBrowser = true) : this(html.ToDataUriString(), browserSettings, requestContext, automaticallyCreateBrowser)
+            IRequestContext requestContext = null, bool automaticallyCreateBrowser = true,
+            Action<IBrowser> onAfterBrowserCreated = null) : this(html.ToDataUriString(), browserSettings, requestContext, automaticallyCreateBrowser, onAfterBrowserCreated)
         {
         }
 
@@ -176,9 +188,15 @@ public ChromiumWebBrowser(HtmlString html, IBrowserSettings browserSettings = nu
         /// <param name="browserSettings">The browser settings to use. If null, the default settings are used.</param>
         /// <param name="requestContext">See <see cref="RequestContext" /> for more details. Defaults to null</param>
         /// <param name="automaticallyCreateBrowser">automatically create the underlying Browser</param>
+        /// <param name="onAfterBrowserCreated">
+        /// Use as an alternative to the <see cref="BrowserInitialized"/> event. If the underlying Chromium Embedded Framework (CEF) browser is created successfully,
+        /// this action is guranteed to be called after the browser created where as the <see cref="BrowserInitialized"/> event may be called before
+        /// you have a chance to subscribe to the event as the CEF Browser is created async. (Issue https://github.com/cefsharp/CefSharp/issues/3552).
+        /// </param>
         /// <exception cref="System.InvalidOperationException">Cef::Initialize() failed</exception>
         public ChromiumWebBrowser(string address = "", IBrowserSettings browserSettings = null,
-            IRequestContext requestContext = null, bool automaticallyCreateBrowser = true)
+            IRequestContext requestContext = null, bool automaticallyCreateBrowser = true,
+            Action<IBrowser> onAfterBrowserCreated = null)
         {
             if (!Cef.IsInitialized)
             {
@@ -194,6 +212,7 @@ public ChromiumWebBrowser(string address = "", IBrowserSettings browserSettings
 
             Cef.AddDisposable(this);
             Address = address;
+            onAfterBrowserCreatedDelegate = onAfterBrowserCreated;
 
             managedCefBrowserAdapter = ManagedCefBrowserAdapter.Create(this, true);
 
@@ -658,6 +677,7 @@ void IRenderWebBrowser.OnVirtualKeyboardRequested(IBrowser browser, TextInputMod
         /// <param name="browser">The browser.</param>
         partial void OnAfterBrowserCreated(IBrowser browser)
         {
+            onAfterBrowserCreatedDelegate?.Invoke(browser);
             BrowserInitialized?.Invoke(this, EventArgs.Empty);
         }