Adds new CefDisplayHandler::OnContentsBoundsChange and
CefDisplayHandler::GetRootWindowScreenRect callbacks.
cefclient: Implement the above callbacks and call
CefBrowserHost::NotifyScreenInfoChanged when the root window
bounds change.
cefclient: osr: Use real screen bounds by default. Pass
`--fake-screen-bounds` for the old default behavior.
Load https://tests/window in cefclient for additional
implementation details and usage examples.
