This also removes an undeclared dependency on mediawiki.Uri.
Bug: T169574
Depends-On: Ic4abaae6e9c74509f7a114a697cdbb78dd1b89b6
Change-Id: I76803da5f1a52171a1af8de1f3e31ea127a2da78
Only shown if VisualEditorEnableDiffPage is set, or query
string param 'visualdiff' is present.
Currently:
* All VE javascript is loaded (could be cut down to just DM code)
* The entire Parsoid HTML of both revisions being compared is loaded
* Both Parsoid HTML docs are parsed into VE DM trees and diffed
Bug: T167508
Change-Id: I151fc9bab3d3032f50c8d11be6b54e45a06fcc34