Add a navigation element to let user switch back from preview to edit mode

When a user edits a page he has three major options in the
left upper corner of the editor window: "Cancel", "Preview"
and "Save". This is fine as these options are the ones which
are used most of the time in this situation.

But in the Preview window there is only the "Save" option.
What I miss here is an "Edit" option to get back to edit mode
as most of the time I switch between "Edit" and "Preview"
mode several times before the page finally can be saved.
A "Cancel" option would also be fine to have in the page
preview mode but it is not as important as "Back to edit"

Currently I use the browser's "Back" button to get back to
the previous page (the editor) but as we all know this is
not really recommended in any web application and I rather
would have navigation provided by the application only and
not mixed between the application and the browser.