* build: enable gn check for //electron:electron_lib
* ci: add gn check step
* ci: set depot_tools path
* chrome_key_systems_provider.h nogncheck
* chore: fix gn check errors on windows
* chore: gn check //electron:electron_app
* fix: use OOIF for webview tag
* fix: do not call GetNativeView for webview
* fix: OOIPF webview's WebContents is managed by embedder frame
* fix: guest view can not be focused
* fix: clear zoom controller when guest is destroyed
* fix: implement the webview resize event
The webview is no longer a browser plugin with the resize event, use
ResizeObserver instead.
* test: disable failed tests due to OOPIF webview
* fix: embedder can be destroyed earlier than guest
This happens when embedder is manually destroyed.
* fix: don't double attach
* fix: recreate iframe when webview is reattached
* fix: resize event may happen very early
* test: some tests are working after OOPIF webview
* chore: remove unused browser plugin webview code
* fix: get embedder via closure
When the "destroyed" event is emitted, the entry in guestInstances would be
cleared.
* chore: rename browserPluginNode to internalElement
* test: make the visibilityState test more robust
* chore: guestinstance can not work with OOPIF webview
* fix: element could be detached before got response from browser
