When a link is clicked with the middle mouse button, chrome opens a window with
"background-tab" disposition. This is not currently handled in sandbox mode,
causing an api::WebContents to leak leading to eventual crash(since it has no
wrapper).
Also fix the event handler for "-add-new-contents" by having it call
`event.preventDefault()` when the window creation should be cancelled.
Chromium already includes the necessary plumbing to manage the
visibility properties and `visibilitychange` event so this gets rid of
most of our custom logic for `BrowserWindow` and `BrowserView`.
Note that `webview` remains unchanged and is still affected by the issues
listed below.
User facing changes:
- The `document` visibility properties and `visibilitychange` event are
now also updated/fired in response to occlusion changes on macOS. In
other words, `document.visibilityState` will now be `hidden` on macOS
if the window is occluded by another window.
- Previously, `visibilitychange` was also fired by *both* Electron and
Chromium in some cases (e.g. when hiding the window). Now it is only
fired by Chromium so you no longer get duplicate events.
- The visiblity state of `BrowserWindow`s created with `{ show: false }`
is now initially `visible` until the window is shown and hidden.
- The visibility state of `BrowserWindow`s with `backgroundThrottling`
disabled is now permanently `visible`.
This should also fix#6860 (but not for `webview`).
- Allow `api::Window` instances to be created from existing `api::WebContents`.
- Override `WebContentsCreated` and `AddNewContents` to wrap renderer-created
`content::WebContents` into `api::WebContents`.
- For `content::WebContents` that should be displayed in new windows, pass the
wrapped `api::WebContents` object to window manager.
