Along with removing the view source standalone windows and prefs this patch:
1) Re-structures several of the view source tests that were only testing the old
standalone windows to now test view source in tab.
2) Adds support viewSourceUtils.viewSource() to open a browser window when there
aren't any open (for browser toolbox view source).
3) Cleans up some of the API for viewSourceUtils and removes the old deprecated
ways of calling it.
MozReview-Commit-ID: DI6sgZwbCf