Code review comment for lp:~bfiller/webbrowser-app/file-upload

Remaining work items so we can land this:

Main use case to get working well is open gmail in browser and try to add an attachment to a new email message:

phase 1:
- disable failing autopilot tests
- enable multi selection mode
- fix up result list to display multiple objects, need to support multiple types, i.e. a picture and a video. perhaps this can be a simple list with some sort of icon. Need to check with design to see what is desired
- this works correctly in webbrowser-app but doesn't work at all if you run in a webapp (like try to upload photo in gmail webbapp).

phase 2:
- instead of hardcoding "ContentType.Pictures" as the type of content desired, get this information from the browser or default to all content-types
- implement the Source Picker UI (in the design spec) to display the choices of available apps returned by the content-hub. This should be a generic UI component that would probably live in the content-hub or sdk