fix: webview should maximize on requestFullscreen

[zcbenz]

Description of Change

Close #27719.

When entering fullscreen with Element.requestFullscreen in child frames, the parent frame should also enter fullscreen mode too. Chromium handles this for iframes, but not for webviews, as the latter are essentially main frames instead of child frames.

This PR makes sure webviews propagate the fullscreen state to embedder.

Note that the patch itself in this PR is not enough to fix the issue, to fix it we have to make the fullscreen state sync between the webview and its embedder frame, and in Electron we are just manually synchronizing the states. A decent patch should change callers or callees of IsFullscreenForTabOrPending to be aware of outer frames (webviews), but it would require much more refactoring. I think it does not worth such efforts upstreaming the patch to Chromium, because very few people would encounter this problem in Chrome browser and the patch in this PR is very easy to maintain.

Release Notes

Notes: Fix requestFullscreen inside webview does not make the element take fullscreen.

[codebytere]

Is this something we can potentially upstream?

[zcbenz]

The patch itself is not enough to fix the issue, so we can not upstream it directly.

To fix the problem we also have to make the fullscreen state sync between the webview and its embedder frame, and in Electron we are just manually synchronizing the states. A decent patch should change callers or callees of IsFullscreenForTabOrPending to be aware of outer frames (webviews), but it would require much more refactoring.

So I think it does not worth such efforts upstreaming the changes to Chromium, as very few people would encounter this problem in Chrome browser and the patch in this PR is very easy to maintain.

[miniak]

There is still one issue, when you exit window fullscreen by clicking the green semaphore button on Mac, the webview's webContents does not exit HTML fullscreen mode. It works propertly for iframes.

[miniak]

I still need this workaround to make it work fully

app.on('web-contents-created', (event, webContents) => {
  webContents.on('enter-html-full-screen', () => {
    if (webContents.getType() === 'webview') {
      const window = webContents.getOwnerBrowserWindow();
      window.once('leave-html-full-screen', () => {
        webContents.executeJavaScript('document.exitFullscreen()', true);
      });
    }
  });
});

[zcbenz]

@miniak The mentioned problem should have been fixed, can you test again?

[miniak]

it works now!

[release-clerk]

Release Notes Persisted

Fix requestFullscreen inside webview does not make the element take fullscreen.

[trop]

I have automatically backported this PR to "13-x-y", please check out #29987

[trop]

I have automatically backported this PR to "12-x-y", please check out #29988

[trop]

I have automatically backported this PR to "14-x-y", please check out #29989

[TranceGeniK]

Is there a way to prevent that behavior ?
It may be preferable in some cases to have the fullscreen limited to the webview container.