As other widgets may be interested in the image info, this should
be part of the DM node, which the media edit dialog then fetches
and uses to populate the MediaSizeWidget.
Other fixes:
* Remove spinner, not really necessary as the orignal size button is
disabled if the orignal dimensions aren't set.
* Don't wait until image info call to resolve to initialise size
widget values. These should always be available instantly from the
attributes.
Depends on I9530ed4257e88b in core.
Change-Id: I394f49941b621059bc08c8a8f79471b2fe16c7d8
Using the MW APIs get a resized version of the image and use
GeneratedContentNode to cache the url.
Bug: 55697
Change-Id: I418f7e1464663f447d46de7ffc29aa5f52d23b12
