Add signals and attributes for datagrid mobile mode

Review Request #8132 — Created April 27, 2016 and submitted — Latest diff uploaded

Information

Djblets
release-0.9.x
9916c48...

Reviewers

Datagrids now represent their current mobile state through the
data-datagrid-mobile-mode attribute. When the datagrid changes modes,
it will update that attribute and fire the mobileModeToggle signal with
an object that indicates wether it was enabled or disabled.

Tested this with an upcoming change in Splat.