Freshen restored stacks, more UX bug fixes.

When restoring a persisted stack, such as last location or a location
where save occurred, freshen the DocumentStack to get the latest
details from backend, and ensure the path is still valid.

Filter Recent directories in create mode based on roots allowed by
incoming request.

Remember when user last picked an external app, and open drawer next
time user launches for GET_CONTENT.

Fix state list drawable ordering, and avoid clobbering Drawable
callback when wrapping in InsetDrawable; tricksy hobbitses!

Make grid items smaller to always fit two columns on phones.  Draw
grid items all the way to screen edge; don't clip to padding.  Better
error message when folder creation failed.  Show Recents in grid mode
when picking any visual content, not just images.

Bug: 10846100, 10903211, 10898993, 10892808, 10892058, 10892009, 10885012
Change-Id: Ia0f88d911abc6ea03645d6fd3e04271c21d5936a