Infrastructure to support for per-window private browsing
(part 1 for #1)
Get source window for context menu actions
(part 2 for #1)
Cleanup context menu-related things after menu will be closed
(part 3 for #1)
Image info: correctly count for duplicate image links
Pass source window to "service"
(part 4 for #1)
Remember private state and use cached value, if source window was closed
(part 5 for #1)
Append "(Private Browsing)" to dialog title
(part 6 for #1)
Add "ownWindow.cropFileNameInTitle" preference
Open new window for same URI and referrer, but different private state
(part 7 for #1)