We don't create a ChromeProcess in headless-browser, so it is currently
not increasing it's open file limit. This is causing crashes on macOS,
which has a very low default limit.
Currently, if we want to add a new e.g. WebContent command line option,
we have to add it to all of Qt, AppKit, and headless-browser. (Or worse,
we only add it to one of these, and we have feature disparity).
To prevent this, this moves command line flags to WebView::Application.
The flags are assigned to ChromeOptions and WebContentOptions structs.
Each chrome can still add its platform-specific options; for example,
the Qt chrome has a flag to enable Qt networking.
There should be no behavior change here, other than that AppKit will now
support command line flags that were previously only supported by Qt.
The default limit (at least on Linux) causes us to run out of file
descriptors at around 15 tabs. Increase this limit to 8k. This is a
rather arbitrary number, but matches the limit set by Chrome.
This allows main UI processes created while there is a currently
running one to request a new tab or a new window with the initial urls
provided on the command line. This matches (almost) the behavior of
Chromium and Firefox.
Add a new IPC protocol between two UI processes. The main UI process
will create an IPC server socket, while secondary UI processes will
connect to that socket and send over the URLs and action it wants the
main process to take.
