alloy: Use Chrome JS dialogs on Windows/Linux (fixes issue #3316)

libcef/browser/alloy/alloy_browser_host_impl.h

@@ -137,12 +137,16 @@ class AlloyBrowserHostImpl : public CefBrowserHostBase,
   // Returns true if windowless rendering is enabled.
   bool IsWindowless() const override;
 
+  bool IsVisible() const override;
+
   // Returns true if this browser supports picture-in-picture.
   bool IsPictureInPictureSupported() const;
 
   // Called when the OS window hosting the browser is destroyed.
   void WindowDestroyed() override;
 
+  bool WillBeDestroyed() const override;
+
   // Destroy the browser members. This method should only be called after the
   // native browser window is not longer processing messages.
   void DestroyBrowser() override;