Expose proper DOM window to the add-on code.
Merge pull request #815 from Gozala/bug/addon-window@820953

Bug 820953 - Expose DOM window to the add-on r=@ochameau
Hotfix regression introduced in previous commit: Bug 820953
Bug 845387: private-browsing isPrivate should take a content script instance
Bug 751378 - Remove unused CAPS strings from stringbundle. r=bz
Merge pull request #853 from erikvold/845387

Bug 845387: private-browsing isPrivate should take a content script instance
Allow page-workers' postMessage to be queued, remove issue from docs