Add new chooser methods to SiteSettingsHandler

This change adds the HandleGetChooserExceptionList and
HandleResetChooserExceptionForSite methods to SiteSettingsHandler to
prepare them for use in site settings. These two methods will eventually
replace the existing HandleFetchUsbDevices and HandleRemoveUsbDevice and
allow future chooser exception types to use them. They will also make it
easier to create Polymer elements to handle chooser exceptions, instead
of the current Polymer element that only handles USB exceptions.

The HandleGetChooserExceptionList will return a list of chooser
exceptions using the new GetChooserExceptionListFromProfile method is
site_settings_helper.h. These new chooser objects will allow the
chooser's site exceptions to be grouped together under the same chooser
object in the UI.  The HandleResetChooserExceptionForSite will reset the
site exception for the given chooser.

Design doc:
https://docs.google.com/document/d/1MPvsrWiVD_jAC8ELyk8njFpy6j1thfVU5aWT3TCWE8w

Bug: 854329
Change-Id: I5536cae3946338b48042087c9b6d6b4abccbebdd
Reviewed-on: https://chromium-review.googlesource.com/c/1321850
Commit-Queue: Ovidio Henriquez <odejesush@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613750}
5 files changed