watermark: Place watermark in the bottom-right when both deltax and deltaty are 0

The default behavior is to replicate the watermark all over the screen but this can
be too intrusive. The repetition is controlled by deltax and deltay and if they are
both 0 the watermark will actually be drawn off-screen and thus not shown.

We take advantage of this to add a special behavior when they are both 0 that simply
places them in the bottom right. This patch doesn't take UI elements into account and
may actually overlay soft-buttons and other chrome.

Change-Id: I4cff1326b8aaecdbc471eaf48e95bc2865181366
(cherry picked from commit 6bfd11dfe4ca41333e990658c45f41fb5e169a41)
Bring back 2 missing methods of Download: add to support pause/resume download by manual feature

Change-Id: Ida89123dc40fa21eff536dbbc43912cd684bcbdb
(cherry picked from commit ecda0270eafcb4485e21645a07f278e9a47a5dd8)
DocumentsUI: fix recursive delete

Create one DirectoryLoader in UI thread to use for delete

Change-Id: I83a5811f152090f7812ad58ff4ee3bc13748d158
(cherry picked from commit d8fbe4953a38f2a57d7116137dceb468f5aca723)