Update rust-azure and rust-layers to their master branches.
auto merge of #736 : metajack/servo/azure-layers-master, r=metajack,me
Fix doubling noncontent_height in float flow
auto merge of #739 : ILyoan/servo/acid1_margin, r=metajack

In `assign_height_inorder_float()`, `base.position.size.height` already counted padding and border, so adding `noncontent_height` to `height` would result in doubling counted padding and border.

By this patch acid1 would be displayed more accurately.

Not sure but maybe width has the same problem, I'll investigate it.
auto merge of #743 : eschweic/servo/dlbi, r=kmcallister

A few changes to the compositor to support invalidate_rect requests from layout.

r? @kmcallister
Stop copying buffers when sending them to quadtrees
Add buffer_map.rs; implement LayerBuffer recycling