Enable Chromium Site Isolation

[amaitland]

CEF recently added support for https://bitbucket.org/chromiumembedded/cef/issues/2498/add-support-for-site-per-process

We should now look at properly supporting the process model as it's now the CEF default.

• Remove process-per-site-instance command line arg from CefSettings

Related issue #2553

[amaitland]

WPF version will require disable-site-isolation-trials command line arg until upstream issue #2789 has been resolved

[amaitland]

https://bitbucket.org/chromiumembedded/cef/issues/2814/process-messages-cant-be-sent-to-all

[amaitland]

Site isolation trials disabled for all WPF/WinForms/OffScreen in commit 93336a0 Now using the default process model (chromium site isolation project)

[amaitland]

WPF version will require disable-site-isolation-trials command line arg until upstream issue #2789 has been resolved

This has been resolved (builds haven't been updated yet)

https://bitbucket.org/chromiumembedded/cef/issues/2814/process-messages-cant-be-sent-to-all

Cannot remove disable-site-isolation-trials until this is solved.

[amaitland]

Issue is now tracked at https://bitbucket.org/chromiumembedded/cef/issues/2849/siteisolation-process-message-from-browser

[amaitland]

Issue has been resolved see https://bitbucket.org/chromiumembedded/cef/issues/2849/siteisolation-process-message-from-browser#comment-60550396

There are potential changes to how frames are handled that need to be evaluated.

[amaitland]

This means that frame objects (including for the main frame) will now always change after cross-origin navigation, and the old frame object will be invalidated.

Cross origin navigations now invalidate the main frame.

[amaitland]

With site isolation enabled many of the tests (pretty much anything that uses the IPC) will fail, so reverting for now and reopening.