Cargoify rust-layers
Merge pull request #103 from metajack/cargoify

Cargoify rust-layers
Revert "Edge tiles should not extend beyond the layer size"

This reverts commit d44454e45ea43e0bc2ae78c69d6a8b22c5dab26b.
Merge pull request #104 from mrobinson/revert-stubby

Revert "Edge tiles should not extend beyond the layer size"
Introduce DevicePixel and use it for layer boundaries

This will mean that Servo can use rust-layers without ambiguity to the
coordinate system of variables and arguments.
Use DevicePixels for TileGrid size

This is the next step in making all units in rust-layers typed.
Store tile_size and calculate BufferRequests in DevicePixels
Store content_offset using typed units