fix: simpleFullScreen exits when web content calls requestFullscreen (#50874)

fix: simpleFullScreen exits when web content calls requestFullscreen

SetHtmlApiFullscreen only checked IsFullscreen() to detect that the
window was already fullscreen, missing the simple-fullscreen case on
macOS. When web content triggered requestFullscreen the code fell
through to SetFullScreen(true) which toggled simple fullscreen off.

Include IsSimpleFullScreen() in the guard so the HTML-API fullscreen
state is updated without touching the window's fullscreen mode.

shell/browser/api/electron_api_web_contents.cc

@@ -4509,7 +4509,8 @@ void WebContents::OnDevToolsSearchCompleted(
 
 void WebContents::SetHtmlApiFullscreen(bool enter_fullscreen) {
   // Window is already in fullscreen mode, save the state.
-  if (enter_fullscreen && owner_window()->IsFullscreen()) {
+  if (enter_fullscreen && (owner_window()->IsFullscreen() ||
+                           owner_window()->IsSimpleFullScreen())) {
     native_fullscreen_ = true;
     UpdateHtmlApiFullscreen(true);
     return;

spec/api-browser-window-spec.ts

@@ -6681,6 +6681,26 @@ describe('BrowserWindow module', () => {
         w.setFullScreen(!w.isFullScreen());
       });
 
+      ifit(process.platform === 'darwin')('does not exit simpleFullScreen when requestFullscreen is called', async () => {
+        const w = new BrowserWindow();
+        await w.loadFile(path.join(fixtures, 'pages', 'a.html'));
+
+        w.setSimpleFullScreen(true);
+        expect(w.isSimpleFullScreen()).to.be.true('isSimpleFullScreen');
+
+        const enterHtmlFS = once(w.webContents, 'enter-html-full-screen');
+        await w.webContents.executeJavaScript('document.getElementById("div").requestFullscreen()', true);
+        await enterHtmlFS;
+
+        expect(w.isSimpleFullScreen()).to.be.true('isSimpleFullScreen after requestFullscreen');
+
+        const leaveHtmlFS = once(w.webContents, 'leave-html-full-screen');
+        await w.webContents.executeJavaScript('document.exitFullscreen()');
+        await leaveHtmlFS;
+
+        expect(w.isSimpleFullScreen()).to.be.true('isSimpleFullScreen after exitFullscreen');
+      });
+
       it('should not be changed by setKiosk method', async () => {
         const w = new BrowserWindow();