feat: Exposing methods required by capturing a hidden webContents

[zeeker999]

Description of Change

This pull request adds methods required by capturing a hidden webContents. With the IncrementCapturerCount(), it's possible to capture screen shot of BrowserView which attached to
a hidden BrowserWindow.

var hiddenWin = new BrowserWindow({ width: 800, height: 600, show: false })
var view = new BrowserView({ webPreferences: { show: true } })

hiddenWin.addBrowserView(view)
view.setBounds({ x: 0, y: 0, width: 800, height: 600})

// view.webContents.capturePage()  works because the browser view is visible initially.

// show the page in a normal window.
var win = new BrowserWindow({ width: 800, height: 600 })
win.removeBrowserView(view)
win.addBrowserView(view)
win.show()

//  the capturePage() works because the browser window is really visible now.

// close the normal window and add the view back to the hidden window.
view.webContents.incrementCapturerCount()
win.removeBrowserView(view)
hiddenWin.addBrowserView(view)
win.close()

// the capturePage() works here because we ask the webContents to ignore the page
// visibility, it wont work without increasing the capturer count.

cc @MarshallOfSound @ckerr @zcbenz

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

notes: Exposing methods required by capturing a hidden webContents。

[welcome]

💖 Thanks for opening this pull request! 💖

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[zeeker999]

Could you please review my changes?

cc @MarshallOfSound @ckerr @zcbenz

[zcbenz]

Can you add documentations for the methods?

[zeeker999]

Ok, no problem.

[zeeker999]

@zcbenz Could you please take another look.

[zcbenz]

This looks good to me, would like to get more inputs from @electron/wg-api.

[zeeker999]

@codebytere I have fixed all issues and pushed to my branch, could you please review my changes again.

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[release-clerk]

Release Notes Persisted

Exposing methods required by capturing a hidden webContents。

[trop]

@LuoJinghua has manually backported this PR to "7-1-x", please check out #21894

[trop]

@LuoJinghua has manually backported this PR to "8-x-y", please check out #21895

[trop]

@LuoJinghua has manually backported this PR to "7-2-x", please check out #21894

[peererror]

is this available for 6.1.x ?